Baseball statistics play an important role in evaluating the progress of a player or team.
Since the flow of a baseball game has natural breaks to it, and normally players act individually rather than performing in clusters, the sport lends itself to easy recordkeeping and statistics. Statistics have been kept for professional baseball since the creation of the National League and American League, now part of Major League Baseball.
Many statistics are also available from outside Major League Baseball, from leagues such as the National Association of Professional Base Ball Players and the Negro Leagues, although the consistency of whether these records were kept, of the standards with respect to which they were calculated, and of their accuracy has varied.
The practice of keeping records of player achievements was started in the 19th century by Henry Chadwick.^{[1]} Based on his experience with the sport of cricket, Chadwick devised the predecessors to modernday statistics including batting average, runs scored, and runs allowed.
Traditionally, statistics such as batting average (the number of hits divided by the number of at bats) and earned run average (the average number of earned runs allowed by a pitcher per nine innings) have dominated attention in the statistical world of baseball. However, the recent advent of sabermetrics has created statistics drawing from a greater breadth of player performance measures and playing field variables. Sabermetrics and comparative statistics attempt to provide an improved measure of a player's performance and contributions to his team from year to year, frequently against a statistical performance average.
Comprehensive, historical baseball statistics were difficult for the average fan to access until 1951, when researcher Hy Turkin published The Complete Encyclopedia of Baseball. In 1969, Macmillan Publishing printed its first Baseball Encyclopedia, using a computer to compile statistics for the first time. Known as "Big Mac", the encyclopedia became the standard baseball reference until 1988, when Total Baseball was released by Warner Books using more sophisticated technology. The publication of Total Baseball led to the discovery of several "phantom ballplayers", such as Lou Proctor, who did not belong in official record books and were removed.^{[2]}
Throughout modern baseball, a few core statistics have been traditionally referenced – batting average, RBI, and home runs. To this day, a player who leads the league in all of these three statistics earns the "Triple Crown". For pitchers, wins, ERA, and strikeouts are the most oftencited statistics, and a pitcher leading his league in these statistics may also be referred to as a "Triple Crown" winner. General managers and baseball scouts have long used the major statistics, among other factors and opinions, to understand player value. Managers, catchers and pitchers use the statistics of batters of opposing teams to develop pitching strategies and set defensive positioning on the field. Managers and batters study opposing pitcher performance and motions in attempting to improve hitting. Scouts will use stats when they are looking at a player who they may end up drafting or signing to a contract.
Some sabermetric statistics have entered the mainstream baseball world that measure a batter's overall performance including onbase plus slugging, commonly referred to as OPS. OPS adds the hitter's onbase percentage (number of times reached base by any means divided by total plate appearances) to his slugging percentage (total bases divided by atbats). Some argue that the OPS formula is flawed and that more weight should be shifted towards OBP (onbase percentage).^{[2]} The statistic wOBA (weighted onbase average) attempts to correct for this.
OPS is also useful when determining a pitcher's level of success. "Opponent Onbase Plus Slugging" (OOPS) is becoming a popular tool to evaluate a pitcher's actual performance. When analyzing a pitcher's statistics, some useful categories to consider include K/9IP (strikeouts per nine innings), K/BB (strikeouts per walk), HR/9 (Home runs per nine innings), WHIP (walks plus hits per inning pitched), and OOPS (opponent onbase plus slugging).
However, since 2001, more emphasis has been placed on DefenseIndependent Pitching Statistics, including DefenseIndependent ERA (dERA), in an attempt to evaluate a pitcher's performance regardless of the strength of the defensive players behind him.
All of the above statistics may be used in certain game situations. For example, a certain hitter's ability to hit lefthanded pitchers might incline a manager to increase his opportunities to face lefthanded pitchers. Other hitters may have a history of success against a given pitcher (or vice versa), and the manager may use this information to create a favorable matchup. Broadcast commentators often refer to this as "playing the percentages".
Most of these terms also apply to softball. Commonly used statistics with their abbreviations are explained here. The explanations below are for quick reference and do not fully or completely define the statistic; for the strict definition, see the linked article for each statistic.
It is difficult to determine quantitatively what is considered to be a "good" value in a certain statistical category, and qualitative assessments may lead to arguments. Using fullseason statistics available at the Official Site of Major League Baseball^{[5]} for the 2004 through 2015 seasons, the following tables show top ranges in various statistics, in alphabetical order. For each statistic, two values are given:


In baseball, an at bat (AB) or time at bat is a batter's turn batting against a pitcher. An at bat is different from a plate appearance. A batter is credited with a plate appearance regardless of what happens during his turn at bat, but a batter is credited with an at bat only if that plate appearance does not have one of the results enumerated below. While at bats are used to calculate certain statistics, including batting average and slugging percentage, a player can qualify for the seasonending rankings in these categories only if he accumulates 502 plate appearances during the season.
A batter will not receive credit for an at bat if his plate appearance ends under the following circumstances:
He receives a base on balls (BB).
He is hit by a pitch (HBP).
He hits a sacrifice fly or a sacrifice bunt (also known as sacrifice hit).
He is awarded first base due to interference or obstruction, usually by the catcher.
He is replaced by another hitter before his at bat is completed, in which case the plate appearance and any related statistics go to the pinch hitter (unless he is replaced with two strikes and his replacement completes a strikeout, in which case the at bat and strikeout are still charged to the first batter).In addition, if the inning ends while he is still at bat (due to the third out being made by a runner caught stealing, for example), no at bat or plate appearance will result. In this case, the batter will come to bat again in the next inning, though the count will be reset to no balls and no strikes.
Rule 9.02(a)(1) of the official rules of Major League Baseball defines an at bat as: "Number of times batted, except that no time at bat shall be charged when a player: (A) hits a sacrifice bunt or sacrifice fly; (B) is awarded first base on four called balls; (C) is hit by a pitched ball; or (D) is awarded first base because of interference or obstruction[.]"
BaseballReference.comBaseballReference.com is a website providing baseball statistics for every player in Major League Baseball history. The site is often used by major media organizations and baseball broadcasters as a source for statistics. It offers a variety of advanced baseball sabermetrics in addition to traditional baseball "counting stats".
BaseballReference.com is part of Sports Reference, LLC; according to an article in Street & Smith's Sports Business Journal, the company's sites have more than 1 million unique users per month.
Batting average (baseball)In baseball, the batting average (BA) is defined by the number of hits divided by at bats. It is usually reported to three decimal places and read without the decimal: A player with a batting average of .300 is "batting threehundred." If necessary to break ties, batting averages could be taken beyond the .001 measurement. In this context, a .001 is considered a "point," such that a .235 batter is 5 points higher than a .230 batter.
Earned runIn baseball, an earned run is any run that was fully enabled by the offensive team's production in the face of competent play from the defensive team. Conversely, an unearned run is a run that would not have been scored without the aid of an error or a passed ball committed by the defense.
An unearned run counts just as much as any other run for the purpose of determining the score of the game. However, it is "unearned" in that it was, in a sense, "given away" by the defensive team.
Both total runs and earned runs are tabulated as part of a pitcher's statistics. However, earned runs are specially denoted because of their use in calculating a pitcher's earned run average (ERA), the number of earned runs allowed by the pitcher per nine innings pitched (i.e., averaged over a regulation game). Thus, in effect, the pitcher is held personally accountable for earned runs, while the responsibility for unearned runs is shared with the rest of the team.
To determine whether a run is earned, the official scorer must reconstruct the inning as it would have occurred without errors or passed balls.
Earned run averageIn baseball statistics, earned run average (ERA) is the average of earned runs given up by a pitcher per nine innings pitched (i.e. the traditional length of a game). It is determined by dividing the number of earned runs allowed by the number of innings pitched and multiplying by nine. Runs resulting from defensive errors (including pitchers' defensive errors) are recorded as unearned runs and omitted from ERA calculations.
Error (baseball)In baseball statistics, an error is an act, in the judgment of the official scorer, of a fielder misplaying a ball in a manner that allows a batter or baserunner to advance one or more bases or allows an at bat to continue after the batter should have been put out. The term error can also refer to the play during which an error was committed.
Games playedGames played (most often abbreviated as G or GP) is a statistic used in team sports to indicate the total number of games in which a player has participated (in any capacity); the statistic is generally applied irrespective of whatever portion of the game is contested.
Hit (baseball)In baseball statistics, a hit (denoted by H), also called a base hit, is credited to a batter when the batter safely reaches first base after hitting the ball into fair territory, without the benefit of an error or a fielder's choice.
Onbase percentageIn baseball statistics, onbase percentage (OBP; sometimes referred to as onbase average/OBA, as the statistic is rarely presented as a true percentage) is a statistic generally measuring how frequently a batter reaches base. Specifically, it records the ratio of the batter's timesonbase (TOB) (the sum of hits, walks, and times hit by pitch) to their number of plate appearances. It first became an official MLB statistic in 1984.
By factoring in only hits, walks and times hit by pitch, OBP does not credit the batter for reaching base due to fielding errors or decisions, as it does not increase when the batter reaches base due to fielding error, fielder's choice, dropped/uncaught third strike, fielder's obstruction, or catcher's interference.
Onbase percentage is added to slugging average to determine onbase plus slugging (OPS). The onbase percentage of all batters faced by one pitcher or team is referred to as onbase against.
Onbase plus sluggingOnbase plus slugging (OPS) is a sabermetric baseball statistic calculated as the sum of a player's onbase percentage and slugging percentage. The ability of a player both to get on base and to hit for power, two important offensive skills, are represented. An OPS of .900 or higher in Major League Baseball puts the player in the upper echelon of hitters. Typically, the league leader in OPS will score near, and sometimes above, the 1.000 mark.
Passed ballIn baseball, a catcher is charged with a passed ball when he fails to hold or control a legally pitched ball that, with ordinary effort, should have been maintained under his control, and, as a result of this loss of control, the batter or a runner on base advances. A runner who advances due to a passed ball is not credited with a stolen base unless he breaks for the base before the pitcher begins his delivery.
Run (baseball)In baseball, a run is scored when a player advances around first, second and third base and returns safely to home plate, touching the bases in that order, before three outs are recorded and all obligations to reach base safely on batted balls are met or assured. A player may score by hitting a home run or by any combination of plays that puts him safely "on base" (that is, on first, second, or third) as a runner and subsequently brings him home. The object of the game is for a team to score more runs than its opponent.
The Official Baseball Rules hold that if the third out of an inning is a force out of a runner advancing to any base then, even if another baserunner crosses home plate before that force out is made, his run does not count. However, if the third out is not a force out, but a tag out, then if that other baserunner crosses home plate before that tag out is made, his run will count. In baseball statistics, a player who advances around all the bases to score is credited with a run (R), sometimes referred to as a "run scored". While runs scored is considered an important individual batting statistic, it is regarded as less significant than runs batted in (RBIs). Both individual runs scored and runs batted in are heavily contextdependent; for a more sophisticated assessment of a player's contribution toward producing runs for his team see runs created.
A pitcher is likewise assessed runs surrendered in his statistics, which differentiate between standard earned runs (for which the pitcher is statistically assigned full responsibility) and unearned runs scored due to fielding errors, which do not count in his personal statistics. Specifically, if a fielding error occurs which affects the number of runs scored in an inning, the Official Scorer – the official ingame statistician – in order to determine how many of the runs should be classified as earned, will reconstruct the inning as if the error had not occurred. For example, with two outs, suppose a runner reaches base because of a fielding error, and then the next batter hits a tworun home run, and then the following batter then makes the third out, ending the inning. If the inning is reconstructed without the error, and if that third batter, instead of reaching on an error, registered an out, the inning would have ended there without any runs scoring. Thus, the two runs that did score will be classified as unearned, and will not count in the pitcher's personal statistics.If a pitching substitution occurs while a runner is on base, and that runner eventually scores a run, the pitcher who allowed the player to get on base is charged with the run even though he was no longer pitching when the run scored.
SabermetricsSabermetrics is the empirical analysis of baseball, especially baseball statistics that measure ingame activity.
Sabermetricians collect and summarize the relevant data from this ingame activity to answer specific questions. The term is derived from the acronym SABR, which stands for the Society for American Baseball Research, founded in 1971. The term "sabermetrics" was coined by Bill James, who is one of its pioneers and is often considered its most prominent advocate and public face.
Save (baseball)In baseball, a save (abbreviated SV or S) is credited to a pitcher who finishes a game for the winning team under certain prescribed circumstances, described below. The number of saves, or percentage of save opportunities successfully converted, is an oftcited statistic of relief pitchers, particularly those in the closer role. It became an official Major League Baseball (MLB) statistic in 1969. Mariano Rivera is MLB's alltime leader in regular season saves with 652.
Slugging percentageIn baseball statistics, slugging percentage (SLG) is a measure of the batting productivity of a hitter. It is calculated as total bases divided by at bats, through the following formula, where AB is the number of at bats for a given player, and 1B, 2B, 3B, and HR are the number of singles, doubles, triples, and home runs, respectively:
Unlike batting average, slugging percentage gives more weight to extrabase hits such as doubles and home runs, relative to singles. Walks are specifically excluded from this calculation, as a plate appearance that ends in a walk is not counted as an at bat.
The name is a misnomer, as the statistic is not a percentage but a scale of measure whose computed value is a number from 0 to 4. The statistic gives a double twice the value of a single, a triple three times the value, and a home run four times.
A slugging percentage is always expressed as a decimal to three decimal places, and is generally spoken as if multiplied by 1000. For example, a slugging percentage of .589 would be spoken as "five eighty nine."
In 2018, the mean average SLG among all teams in Major League Baseball was .409.
Strike zoneIn baseball, the strike zone is the volume of space through which a pitch must pass in order to be called a strike, if the batter does not swing. The strike zone is defined as the volume of space above home plate and between the batter's knees and the midpoint of their torso. Whether a pitch passes through the zone is decided by an umpire, who is generally positioned behind the catcher.
Strikes are desirable for the pitcher and the fielding team, as three strikes result in a strikeout of that batter. A pitch that misses the strike zone is called a ball (only if the batter doesn't swing). Balls are desirable for the batter and the batting team, as four balls allow the batter to take a "walk" to first base as a base on balls.
Triple (baseball)In baseball, a triple is the act of a batter safely reaching third base after hitting the ball, with neither the benefit of a fielder's misplay (see error) nor another runner being put out on a fielder's choice. A triple is sometimes called a "threebagger" or "threebase hit". For statistical and scorekeeping purposes it is denoted by 3B.Triples have become somewhat rare in Major League Baseball. It often requires a ball hit to a distant part of the field, or the ball taking an unusual bounce in the outfield. It also usually requires that the batter hit the ball solidly, and be a speedy runner. It also often requires that the batter's team have a good strategic reason for wanting the batter on third base, as a double will already put the batter in scoring position and there will often be little strategic advantage to taking the risk of trying to stretch a double into a triple. (The insidethepark home run is much rarer than a triple). The trend for modern ballparks is to have smaller outfields (often increasing the number of home runs); it has ensured that the career and season triples leaders mostly consist of those who played early in Major League Baseball history, generally in the deadball era.
A walkoff triple (one that ends a game) occurs very infrequently. For example, the 2016 MLB season saw only three walkoff triples, excluding one play that was actually a triple plus an error.
Wild pitchIn baseball, a wild pitch (WP) is charged against a pitcher when his pitch is too high, too short, or too wide of home plate for the catcher to control with ordinary effort, thereby allowing a baserunner, perhaps even the batterrunner on an uncaught third strike, to advance.
A wild pitch usually passes the catcher behind home plate, often allowing runners on base an easy chance to advance while the catcher chases the ball down. Sometimes the catcher may block a pitch, and the ball may be nearby, but the catcher has trouble finding the ball, allowing runners to advance.
A closely related statistic is the passed ball. As with many baseball statistics, whether a pitch that gets away from a catcher is counted as a wild pitch or a passed ball is at the discretion of the official scorer. The benefit of the doubt is usually given to the catcher if there is uncertainty; therefore, most of these situations are scored as wild pitches. If the pitch was so low as to touch the ground, or so high that the catcher has to jump to get to it, or so wide that the catcher has to lunge for it, it is usually then considered a wild pitch and not a passed ball. Because the pitcher and catcher handle the ball much more than other fielders, certain misplays on pitched balls are defined in Rule 10.13 as wild pitches and passed balls. No error shall be charged when a wild pitch or passed ball is scored.
A wild pitch may only be scored if one or more runners advance. If the bases are empty, or the catcher retrieves the ball quickly and the runner(s) are unable to advance, a wild pitch is not charged. A scored run due to a wild pitch is recorded as an earned run. A runner who advances on a wild pitch is not credited with a stolen base unless he breaks before the pitcher begins his delivery.
Win–loss record (pitching)In baseball and softball, a pitcher's win–loss record (also referred to simply as their record) indicates the number of wins (denoted "W") and losses (denoted "L") they have been credited with. For example, a 20–10 win–loss record would represent 20 wins and 10 losses.
In each game, one pitcher on the winning team is awarded a win (the "winning pitcher") and one pitcher on the losing team is given a loss (the "losing pitcher") in their respective statistics. These pitchers are collectively known as the pitchers of record. The designation of win or loss for a pitcher is known as a decision, and only one pitcher for each team receives a decision. A starting pitcher who does not receive credit for a win or loss is said to have no decision. In certain situations, another pitcher on the winning team who pitched in relief of the winning pitcher can be credited with a save, and holds can be awarded to relief pitchers on both sides, but these are never awarded to the same pitcher who is awarded the win.
The decisions are awarded by the official scorer of the game in accordance with the league's rules. The official scorer does not assign a winning or losing pitcher in some games which are forfeited, such as those that are tied at the time of forfeiture. If the game is tied (a rare event), no pitcher is awarded any decision. A pitcher's winning percentage is calculated by dividing the number of wins by the number of decisions (wins plus losses), and it is commonly expressed with three decimal places.
Major League Baseball records  

Baseball statistics (types of records)  
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Batting leaders 
 
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