A game is played between two teams, each composed of nine players, that take turns playing offense (batting or hitting) and defense (fielding or pitching). A pair of turns, one at bat and one in the field, by each team constitutes an inning; there are nine innings in a game. One team—customarily the visiting team—bats in the top, or first half, of every inning; the other team—customarily the home team—bats in the bottom, or second half, of every inning. The goal of a game is to score more points (runs) than the other team. The players on the team at bat attempt to score runs by circling, or completing a tour of, the four bases set at the corners of the square-shaped baseball diamond. A player bats at home plate and must proceed counterclockwise to first base, second base, third base, and back home in order to score a run. The team in the field attempts both to prevent runs from scoring and to record outs, which remove opposing players from offensive action until their turn in their team’s batting order comes up again. When three outs are recorded, the teams switch roles for the next half-inning. If the score of the game is tied after nine innings, extra innings are played to resolve the contest. Children’s games are often scheduled for fewer than nine innings. Diagram of a baseball field (the term diamond may be used to refer to the square area defined by the four bases or to the entire playing field). The dimensions given are for professional and professional-style games; children often play on smaller fields. The game is played on a field whose primary boundaries, the foul lines, extend forward from home plate at 45-degree angles. The 90-degree area within the foul lines is referred to as fair territory; the 270-degree area outside them is foul territory. The part of the field enclosed by the bases and several yards beyond them is the infield; the area farther beyond the infield is the outfield. In the middle of the infield is a raised pitcher’s mound, with a rectangular rubber plate (the rubber) at its center. The outer boundary of the outfield is typically demarcated by a raised fence, which may be of any material and height (many amateur games are played on fields without a fence). Fair territory between home plate and the outfield boundary is baseball’s field of play, though significant events can take place in foul territory, as well. There are three basic tools of baseball: the ball, the bat, and the glove or mitt. The baseball is about the size of an adult’s fist, around 9 inches (23 centimeters) in circumference. It has a rubber or cork center, wound in yarn and covered in white cowhide, with red stitching. The bat is a hitting tool, traditionally made of a single, solid piece of wood; other materials are now commonly used for nonprofessional games. It is a hard round stick, about 2.5 inches (6.4 centimeters) in diameter at the hitting end, tapering to a narrower handle and culminating in a knob. Bats used by adults are typically around 34 inches (86 centimeters) long, and not longer than 42 inches (106 centimeters). The glove or mitt is a fielding tool, made of padded leather with webbing between the fingers. As an aid in catching and holding onto the ball, it takes various shapes to meet the specific needs of different fielding positions. Protective helmets are also standard equipment for all batters. At the beginning of each half-inning, the nine players on the fielding team arrange themselves around the field. One of them, the pitcher, stands on the pitcher’s mound; the pitcher begins the pitching delivery with one foot on the rubber, pushing off it to gain velocity when throwing toward home plate. Another player, the catcher, squats on the far side of home plate, facing the pitcher. The rest of the team faces home plate, typically arranged as four infielders—who set up along or within a few yards outside the imaginary lines between first, second, and third base—and three outfielders. In the standard arrangement, there is a first baseman positioned several steps to the left of first base, a second baseman to the right of second base, a shortstop to the left of second base, and a third baseman to the right of third base. The basic outfield positions are left fielder, center fielder, and right fielder. A neutral umpire sets up behind the catcher.


Game play starts with a batter standing at home plate, holding a bat. The batter waits for the pitcher to throw a pitch (the ball) toward home plate, and attempts to hit the ball with the bat. The catcher catches pitches that the batter does not hit—as a result of either electing not to swing or failing to connect—and returns them to the pitcher. A batter who hits the ball into the field of play must drop the bat and begin running toward first base, at which point the player is referred to as a runner (or, until the play is over, a batter-runner). A batter-runner who reaches first base without being put out (see below) is said to be safe and is now on base. A batter-runner may choose to remain at first base or attempt to advance to second base or even beyond—however far the player believes can be reached safely. A player who reaches base despite proper play by the fielders has recorded a hit. A player who reaches first base safely on a hit is credited with a single. If a player makes it to second base safely as a direct result of a hit, it is a double; third base, a triple. If the ball is hit in the air within the foul lines over the entire outfield (and outfield fence, if there is one), it is a home run: the batter and any runners on base may all freely circle the bases, each scoring a run. This is the most desirable result for the batter. A player who reaches base due to a fielding mistake is not credited with a hit—instead, the responsible fielder is charged with an error. Any runners already on base may attempt to advance on batted balls that land, or contact the ground, in fair territory, before or after the ball lands; a runner on first base must attempt to advance if a ball lands in play. If a ball hit into play rolls foul before passing through the infield, it becomes dead and any runners must return to the base they were at when the play began. If the ball is hit in the air and caught before it lands, the batter has flied out and any runners on base may attempt to advance only if they tag up or touch the base they were at when the play began, as or after the ball is caught. Runners may also attempt to advance to the next base while the pitcher is in the process of delivering the ball to home plate—a successful effort is a stolen base. A pitch that is not hit into the field of play is called either a strike or a ball. A batter against whom three strikes are recorded strikes out. A batter against whom four balls are recorded is awarded a base on balls or walk, a free advance to first base. (A batter may also freely advance to first base if any part of the batter’s body or uniform is struck by a pitch before the batter either swings at it or it contacts the ground.) Crucial to determining balls and strikes is the umpire’s judgment as to whether a pitch has passed through the strike zone, a conceptual area above home plate extending from the midpoint between the batter’s shoulders and belt down to the hollow of the knee. A strike is called when one of the following happens: The batter lets a well-pitched ball (one within the strike zone) go through to the catcher. The batter swings at any ball (even one outside the strike zone) and misses. The batter hits a foul ball—one that either initially lands in foul territory or initially lands within the diamond but moves into foul territory before passing first or third base. If there are already two strikes on the batter, a foul ball is not counted as a third strike thus, a foul ball cannot result in the immediate strikeout of the batter. (There is an exception to this exception: a two-strike foul bunt is recorded as a third strike.) A ball is called when the pitcher throws a pitch that is outside the strike zone, provided the batter has not swung at it. A shortstop tries to tag out a runner who is sliding headfirst, attempting to reach second base. While the team at bat is trying to score runs, the team in the field is attempting to record outs. Among the various ways a member of the batting team may be put out, five are most common: The strikeout: as described above, recorded against a batter who makes three strikes before putting the ball into play or being awarded a free advance to first base. The flyout: as described above, recorded against a batter who hits a ball in the air that is caught by a fielder, whether in fair territory or foul territory, before it lands, whether or not the batter has run. The ground out: recorded against a batter (in this case, batter-runner) who hits a ball that lands in fair territory which, before the batter-runner can reach first base, is retrieved by a fielder who touches first base while holding the ball or relays it to another fielder who touches first base while holding the ball. The force out: recorded against a runner who is required to attempt to advance—either because the runner is on first base and a batted ball lands in fair territory, or because the runner immediately behind on the basepath is thus required to attempt to advance—but fails to reach the next base before a fielder touches the base while holding the ball. The ground out is technically a special case of the force out. The tag out: recorded against a runner who is touched by a fielder with the ball or a glove holding the ball, while the runner is not touching a base. It is possible to record two outs in the course of the same play—a double play; even three—a triple play—is possible, though this is very rare. Players put out or retired must leave the field, returning to their team’s dugout or bench. A runner may be stranded on base when a third out is recorded against another player on the team. Stranded runners do not benefit the team in its next turn at bat—every half-inning begins with the bases empty of runners. An individual player’s turn batting or plate appearance is complete when the player reaches base (or hits a home run), makes an out, or hits a ball that results in the team’s third out, even if it is recorded against a teammate. On rare occasions, a batter may be at the plate when, without the batter’s hitting the ball, a third out is recorded against a teammate—for instance, a runner getting caught stealing (tagged out attempting to steal a base). A batter with this sort of incomplete plate appearance starts off the team’s next turn batting; any balls or strikes recorded against the batter the previous inning are erased. A runner may circle the bases only once per plate appearance and thus can score at most a single run per batting turn. Once a player has completed a plate appearance, that player may not bat again until the eight other members of his team have all taken their turn at bat. The batting order is set before the game begins, and may not be altered except for substitutions. Once a player has been removed for a substitute, that player may not reenter the game. Children’s games often have more liberal substitution rules. If the designated hitter (DH) rule is in effect, each team has a tenth player whose sole responsibility is to bat (and run). The DH takes the place of another player—almost invariably the pitcher—in the batting order, but does not field. Thus, even with the DH, each team still has a batting order of nine players and a fielding arrangement of nine players.


Relief pitchers warming up, overseen by a bullpen coach. A manager will often have both a right-handed and a left-handed reliever warm up to maximize his strategic options. Roster, or squad, sizes differ between different leagues and different levels of organized play. Major League Baseball teams maintain twenty-five-player active rosters. A typical twenty-five-man roster in a league without the DH rule, such as MLB’s National League, features:
  • eight position players—catcher, four infielders, three outfielders—who play on a regular basis
  • five starting pitchers who constitute the team’s pitching rotation or starting rotation
  • six relief pitchers, including one specialist closer, who constitute the team’s bullpen (named for the off-field area where pitchers warm up)
  • one backup, or substitute, catcher
  • two backup infielders
  • two backup outfielders
  • one specialist pinch hitter, or a second backup catcher, or a seventh reliever


The manager, or head coach of a team, oversees the team’s major strategic decisions, such as establishing the starting rotation, setting the lineup, or batting order, before each game, and making substitutions during games—in particular, bringing in relief pitchers. Managers are typically assisted by two or more coaches; they may have specialized responsibilities, such as working with players on hitting, fielding, pitching, or strength and conditioning. At most levels of organized play, two coaches are stationed on the field when the team is at bat: the first base coach and third base coach, occupying designated coaches’ boxes just outside the foul lines, assist in the direction of base runners when the ball is in play, and relay tactical signals from the manager to batters and runners during pauses in play. In contrast to many other team sports, baseball managers and coaches generally wear their team’s uniforms; coaches must be in uniform in order to be allowed on the playing field during a game. Any baseball game involves one or more umpires, who make rulings on the outcome of each play. At a minimum, one umpire will stand behind the catcher, to have a good view of the strike zone, and call balls and strikes. Additional umpires may be stationed near the other bases, thus making it easier to judge plays such as attempted force outs and tag outs. In Major League Baseball, four umpires are used for each game, one near each base. In the playoffs, six umpires are used: one at each base and two in the outfield along the foul lines.


Many of the pre-game and in-game strategic decisions in baseball revolve around a fundamental fact: in general, right-handed batters tend to be more successful against left-handed pitchers and, to an even greater degree, left-handed batters tend to be more successful against right-handed pitchers. A manager with several left-handed batters in the regular lineup who knows the team will be facing a left-handed starting pitcher may respond by starting one or more of the right-handed backups on the team’s roster. During the late innings of a game, as relief pitchers and pinch hitters are brought in, the opposing managers will often go back and forth trying to create favorable matchups with their substitutions: the manager of the fielding team trying to arrange same-handed pitcher-batter matchups, the manager of the batting team trying to arrange opposite-handed matchups. With a team that has the lead in the late innings, a manager may remove a starting position player—especially one whose turn at bat is not likely to come up again—for a more skillful fielder.


A first baseman receives a pickoff throw, as the runner dives back to first base. The tactical decision that precedes almost every play in a baseball game involves pitch selection. Among the wide variety of pitches that may be thrown, the four basic types are the fastball, the changeup (or off-speed pitch), and two breaking balls—the curveball and the slider. Pitchers have different repertoires of pitches they are skillful at throwing. Conventionally, before each pitch, the catcher signals the pitcher what type of pitch to throw, as well as its general vertical and/or horizontal location. If there is disagreement on the selection, the pitcher may shake off the sign and the catcher will call for a different pitch. With a runner on base and taking a lead, the pitcher may attempt a pickoff, a quick throw to a fielder covering the base to keep the runner’s lead in check or, optimally, effect a tag out. If an attempted stolen base is anticipated, the catcher may call for a pitchout, a ball thrown deliberately off the plate, allowing the catcher to catch it while standing and throw quickly to a base. Facing a batter with a strong tendency to hit to one side of the field, the fielding team may employ a shift, with most or all of the fielders moving to the left or right of their usual positions. With a runner on third base, the infielders may play in, moving closer to home plate to improve the odds of throwing out the runner on a ground ball, though a sharply hit grounder is more likely to carry through a drawn-in infield.


A batter squares to bunt, moving his hands up the barrel of the bat to increase his control and deaden the ball on impact. Several basic offensive tactics come into play with a runner on first base, including the fundamental choice of whether to attempt a steal of second base. The hit and run is sometimes employed with a skillful contact hitter: the runner takes off with the pitch drawing the shortstop or second baseman over to second base, creating a gap in the infield for the batter to poke the ball through. The sacrifice bunt calls for the batter to focus on making contact with the ball so that it rolls a short distance into the infield, allowing the runner to advance into scoring position even at the expense of the batter being thrown out at first—a batter who succeeds is credited with a sacrifice. (A batter, particularly one who is a fast runner, may also attempt to bunt for a hit.) A sacrifice bunt employed with a runner on third base, aimed at bringing that runner home, is known as a squeeze play. With a runner on third and fewer than two outs, a batter may instead concentrate on hitting a fly ball that, even if it is caught, will be deep enough to allow the runner to tag up and score—a successful batter in this case gets credit for a sacrifice fly. The manager will sometimes signal a batter who is ahead in the count (i.e., has more balls than strikes) to take, or not swing at, the next pitch.


Baseball has certain attributes that set it apart from the other popular team sports in the countries where it is has a following, games such as American and Canadian football, basketball, ice hockey, and soccer. All of these sports use a clock; in all of them, game play is less individual and more collective; and in none of them is the variation between playing fields nearly as substantial or important. The comparison between cricket and baseball demonstrates that many of baseball’s distinctive elements are shared in various ways with its cousin sport.


In clock-limited sports, games often end with a team that holds the lead killing the clock rather than competing aggressively against the opposing team. In contrast, baseball has no clock; a team cannot win without getting the last batter out and rallies are not constrained by time. At almost any turn in any baseball game, the most advantageous strategy is some form of aggressive strategy. In contrast, again, the clock comes into play even in the case of multi-day Test and first-class cricket: the possibility of a draw often encourages a team that is batting last and well behind to bat defensively, giving up any faint chance at a win to avoid a loss. Baseball offers no such reward for conservative batting. While nine innings has been the standard since the beginning of professional baseball, the duration of the average major league game has increased steadily through the years. At the turn of the twentieth century, games typically took an hour and a half to play. In the 1920s, they averaged just less than two hours, which eventually ballooned t 2:38 in 1960. By 1997, the average American League game lasted 2:57 (National League games were about 10 minutes shorter—pitchers at the plate making for quicker outs than designated hitters). In 2004, Major League Baseball declared that its goal was an average game of merely 2:45. The lengthening of games is attributed to longer breaks between half-innings for television commercials, increased offense, more pitching changes, and a slower pace of play with pitchers taking more time between each delivery, and batters stepping out of the box more frequently. Other leagues have experienced similar issues; in 2008, Nippon Professional Baseball took steps aimed at shortening games by 12 minutes from the preceding decade’s average of 3:18.


For a team sport, baseball places individual players under unusual scrutiny and pressure. In 1915, a baseball instructional manual pointed out that every single pitch, of which there are often more than two hundred in a game, involves an individual, one-on-one contest: “the pitcher and the batter in a battle of wits”. Contrasting the game with both football and basketball, scholar Michael Mandelbaum argues that “baseball is the one closest in evolutionary descent to the older individual sports”. Pitcher, batter, and fielder all act essentially independent of each other. While coaching staffs can signal pitcher or batter to pursue certain tactics, the execution of the play itself is a series of solitary acts. If the batter hits a line drive, the outfielder is solely responsible for deciding to try to catch it or play it on the bounce and for succeeding or failing. The statistical precision of baseball is both facilitated by this isolation and reinforces it. As described by Mandelbaum, It is impossible to isolate and objectively assess the contribution each [football] team member makes to the outcome of the play…. [E]very basketball player is interacting with all of his teammates all the time. In baseball, by contrast, every player is more or less on his own. Baseball is therefore a realm of complete transparency and total responsibility. A baseball player lives in a glass house, and in a stark moral universe…. Everything that every player does is accounted for and everything accounted for is either good or bad, right or wrong.


Unlike those of most sports, baseball playing fields can vary significantly in size and shape. While the dimensions of the infield are specifically regulated, the only constraint on outfield size and shape for professional teams following the rules of Major League and Minor League Baseball is that fields built or remodeled since June 1, 1958, must have a minimum distance of 325 feet (99 m) from home plate to the fences in left and right field and 400 feet (122 m) to center. Major league teams often skirt even this rule. For example, at Minute Maid Park, which became the home of the Houston Astros in 2000, the Crawford Boxes in left field are only 315 feet (96 m) from home plate. There are no rules at all that address the height of fences or other structures at the edge of the outfield. The most famously idiosyncratic outfield boundary is the left-field wall at Boston’s Fenway Park, in use since 1912: the Green Monster is 310 feet (94 m) from home plate down the line and 37 feet (11 m) tall. View of Fenway Park, home of the Boston Red Sox, from behind third base. The Green Monster is visible at the far left. Similarly, there are no regulations at all concerning the dimensions of foul territory. Thus a foul fly ball may be entirely out of play in a park with little space between the foul lines and the stands, but a flyout in a park with more expansive foul ground. A fence in foul territory that is close to the outfield line will tend to direct balls that strike it back toward the fielders, while one that is farther away may actually prompt more collisions, as outfielders run full speed to field balls deep in the corner; these variations can make the difference between a double and a triple or inside-the-park home run. The surface of the field is also unregulated. While the diagram in theRules and game play section above shows a traditional field surfacing arrangement (and the one used by virtually all MLB teams with naturally surfaced fields), teams are free to decide what areas will be grassed or bare. Some fields—including several in MLB—use an artificial surface, such as Astroturf. Surface variations can have a significant effect on how ground balls behave and are fielded as well as on base running. Similarly, the presence of a roof (seven major league teams play in stadiums with permanent or retractable roofs) can greatly affect how fly balls are played. While football and soccer players deal with similar variations of field surface and stadium covering, the size and shape of their fields are much more standardized; the area out-of-bounds on a football or soccer field does not affect gameplay the way foul territory in baseball does, so variations in that regard are largely insignificant. These physical variations create a distinctive set of playing conditions at each ballpark. Other local factors, such as altitude and climate, can also significantly affect gameplay. A given stadium may acquire a reputation as a pitcher’s park or a hitter’s park, if one or the other discipline notably benefits from its unique mix of elements. The most exceptional park in this regard is Coors Field, home of the Colorado Rockies. Its high altitude—5,282 feet (1,610 m) above sea level—is responsible for giving it the strongest hitter’s park effect in the major leagues. Wrigley Field, home of the Chicago Cubs, is known for its fickle disposition: a hitter’s park when the strong winds off Lake Michigan are blowing out, it becomes more of a pitcher’s park when they are blowing in. The absence of a standardized field affects not only how particular games play out, but the nature of team rosters and players’ statistical records. For example, hitting a fly ball 330 feet (100 m) into right field might result in a easy catch on the warning track at one park, and a home run at another. A team that plays in a park with a relatively short right field, such as the New York Yankees, will tend to stock its roster with left-handed pull hitters, who can best exploit it. On the individual level, a player who spends most of his career with a team that plays in a hitter’s park will gain an advantage in batting statistics over time—even more so if his talents are especially suited to the park.


Organized baseball lends itself to statistics to a greater degree than many other sports. Each play is discrete and has a relatively small number of possible outcomes. In the late nineteenth century, a former cricket player, English-born Henry Chadwick of Brooklyn, New York, was responsible for the “development of the box score, tabular standings, the annual baseball guide, the batting average, and most of the common statistics and tables used to describe baseball.” The statistical record is so central to the game’s “historical essence” that Chadwick came to be known as Father Baseball. In the 1920s, American newspapers began devoting more and more attention to baseball statistics, initiating what journalist and historian Alan Schwarz describes as a “tectonic shift in sports, as intrigue that once focused mostly on teams began to go to individual players and their statistics lines.” The Official Baseball Rules administered by Major League Baseball require the official scorer to categorize each baseball play unambiguously. The rules provide detailed criteria to promote consistency. The score report is the official basis for both the box score of the game and the relevant statistical records. General managers, managers, and baseball scouts use statistics to evaluate players and make strategic decisions. Certain traditional statistics are familiar to most baseball fans. The basic batting statistics include:
  • At bats: plate appearances, excluding walks and hit by pitches—where the batter’s ability is not fully tested—and sacrifices and sacrifice flies—where the batter intentionally makes an out in order to advance one or more base runners
  • Hits: times reached base because of a batted, fair ball without fielding error or fielder’s choice
  • Runs: times circling the bases and reaching home safely
  • Runs batted in (RBIs): number of runners who scored due to a batter’s action (including the batter, in the case of a home run), except when batter grounded into double play or reached on an error
  • Home runs: hits on which the batter successfully touched all four bases, without the contribution of a fielding error
  • Batting average: hits divided by at bats—the traditional measure of batting ability
The basic base running statistics include:
  • Stolen bases: times advancing to the next base entirely due to the runner’s own efforts, generally while the pitcher is preparing to deliver or delivering the ball
  • Caught stealing: times tagged out while attempting to steal a base
Cy Young—the holder of many major league career marks, including wins and innings pitched, as well as losses—in 1908. MLB’s annual awards for the best pitcher in each league are named for Young. The basic pitching statistics include:
  • Wins: games where pitcher was pitching while his team took a lead that it never relinquished, going on to win
  • Losses: games where pitcher was pitching while the opposing team took a lead that it never relinquished, going on to win
  • Saves: games where the pitcher enters a game led by the pitcher’s team, finishes the game without surrendering the lead, is not the winning pitcher, and either (a) the lead was three runs or less when the pitcher entered the game; (b) the potential tying run was on base, at bat, or on deck; or (c) the pitcher pitched three or more innings
  • Innings pitched: outs recorded while pitching divided by three
  • Strikeouts: times pitching three strikes to a batter
  • Winning percentage: wins divided by decisions (wins plus losses)
  • Earned run average (ERA): runs allowed, excluding those resulting from fielding errors, per nine innings pitched
The basic fielding statistics include:
  • Putouts: times the fielder catches a fly ball, tags or forces out a runner, or otherwise directly effects an out
  • Assists: times a putout by another fielder was recorded following the fielder touching the ball
  • Errors: times the fielder fails to make a play that should have been made with common effort, and the batting team benefits as a result
  • Total chances: putouts plus assists plus errors
  • Fielding average: successful chances (putouts plus assists) divided by total chances
Among the many other statistics that are kept are those collectively known assituational statistics. For example, statistics can indicate which specific pitchers a certain batter performs best against. If a given situation statistically favors a certain batter, the manager of the fielding team may be more likely to change pitchers or have the pitcher intentionally walk the batter in order to face one who is less likely to succeed.


Sabermetrics refers to the field of baseball statistical study and the development of new statistics and analytical tools. The term is also used to refer directly to new statistics themselves. The term was coined around 1980 by one of the field’s leading proponents, Bill James, and derives from the Society for American Baseball Research (SABR). The growing popularity of sabermetrics since the early 1980s has brought more attention to two batting statistics that sabermetricians argue are much better gauges of a batter’s skill than batting average:
  • On-base percentage measures a batter’s ability to get on base. It is calculated by taking the sum of the batter’s successes in getting on base (hits plus walks plus hit by pitches) and dividing that by the batter’s total plate appearances (at bats plus walks plus hit by pitches plus sacrifice flies), except for sacrifice bunts.
  • Slugging percentage measures a batter’s ability to hit for power. It is calculated by taking the batter’s total bases (one per each single, two per double, three per triple, and four per home run) and dividing that by the batter’s at bats.
  • Some of the new statistics devised by sabermetricians have gained wide use:
  • On-base plus slugging (OPS) measures a batter’s overall ability. It is calculated by adding the batter’s on-base percentage and slugging percentage.
  • Walks plus hits per inning pitched (WHIP) measures a pitcher’s ability at preventing hitters from reaching base. It is calculated exactly as its name suggests.