In baseball, it is crucial to know how to routinely field a grounder before you can learn how to turn a double play. In the same way with statistics, understanding the basics is necessary before learning more advanced metrics. These basic baseball statistics are ones that have been around since even before Babe Ruth’s time. A fundamental understanding of baseball and/or experience playing at any level will likely have allowed exposure to most or all of these statistics. This may serve as a good refresher if it has been awhile, or if just now working into some of the more complicated metrics. This article will serve as a quick learning course for the basics.
Plate Appearance |PA|
A plate appearance occurs any time a batter steps to the plate and the appearance ends with the batter completing his turn in batting (i.e. is out or becomes a runner). While plate appearances are not used in the calculation of any official MLB statistics, their use is crucial in many advanced player and team projection systems. Plate appearances are used for projection systems due to their ability to paint a fuller picture of a batter’s efforts at the plate. As we will see, PAs exclude less outcomes than their alternative and as such include more plays that the batter is involved in.
For projection purposes, a “full season” of plate appearances is defined as 600 plate appearances. As the season is 162 games, this leads to an average of around 3.7 plate appearances a game. Very few players actually play in all 162 games due to injury, fatigue, etc. and so this number ends up being closer to 4 PA/G. It is important to note that the 600 value does not take into account batting order position, injury risk, etc. and as such functions as a baseline for player projection comparisons.
An at-bat occurs any time a batter comes to the plate, and the plate appearance does not end in a walk, hit-by-pitch, sacrifice, sacrifice fly, or some other award of first base (due to interference, etc.). The calculation of batting average, on-base percentage, and slugging percentage all use at-bats in their formulae. ABs are preferable for calculating these percentages because they do not penalize a player for his ability to draw walks, hit-by-pitches, or advance runners through sacrifice plays.
As mentioned above, at-bats are not preferable for making player projections. ABs do not represent the results of walks, hit-by-pitches, etc.. This causes an inadequacy in projecting player ability.
The same definition as hits counted against a pitcher; When a batter bats the ball into play and successfully reaches base without a defensive error, a hit is awarded. Hits are the main way batters reach base, but on their own the statistic is not indicative of much. Without the game context, at-bat total, or total bases earned, hits are mostly meaningless. They are unable to tell us the results or signal the presence of a repeatable skill in a certain circumstance.
Walks, abbreviated as BB (for base [awarded] on balls), depict the number of a times a batter is awarded first base due to working 4 balls from a pitcher in a plate appearance. Walks are an indication of a batter’s “eye” or patience at the plate, i.e. his ability to withhold from swinging at bad or un-hittable pitches outside the strike zone.
Strikeouts |SO or K|
A batter earns a strikeout each time a pitcher throws 3 strikes against him in a plate appearance, and the batter is thus ruled “out”. In rare cases the batter may reach first base due to a third strike dropped by the catcher and not be ruled out, but still earns a strikeout. Strikeouts are another way to observe a batter’s patience at the plate. Hitters with high strikeout numbers may swing at many more pitches (both hittable and unhittable) than more patient hitters with lower strikeout numbers.
While strikeouts are an undesirable statistic to earn, even some of the best hitters in the MLB have high strikeout numbers. Due to their great skill in hitting, they are more confident in hitting a wide array of pitches, instead of only specific types of pitches. Because they are swinging more, they also miss more pitches (in the absolute sense of the word). This leads to more strikes thrown, and from this, more strikeouts. While strikeouts are bad, there may be more to the overall story of a specific batter’s talent.
Hit-By-Pitch (also Hit Batsmen) |HBP|
A batter earns a HBP each time he is struck with a pitcher’s pitch without attempting to swing at the pitch (including making bat contact with the ball). After a HBP, the batter is awarded first base. Batters who “crowd” the plate by standing on the inner edge of the batter’s box are most likely to accrue hit-by-pitches.
Aside from the injury risk associated with them, HBP are functionally the same as walks in that the batter is able to reach first base without putting the ball in play. As we will see later, the fact that walks and HBPs are weighted similar in terms of run expectancy supports this.
Singles are hits in which the batter reaches first base. A large majority of a batter’s hits will be singles. There are a variety of hits that might end up as singles, among them are: batted balls that land in the outfield in front of the outfielder, grounders that get past an infielder, infield singles that are hit at an infielder but due to speed the batter reaches first, etc.
Doubles, as you might be able to infer, are hits in which the batter ends up at second base. A double can be indicative of a fast-running batter (one who is able to “stretch” a single into a double due to his speed) or a powerful hitter (one who is able to hit a ball that reaches the wall of the outfield, generally a sure-fire double).
Following a natural progression, triples are hits in which the batter reaches third base. Triples are unquestionably the hardest hit to earn as from 2010-2015, triples accounted for around 0.50% of all hits, far less than the other types (1B: ~91.5%, 2B: ~5%, HR: ~3%). Triples are so difficult because they require a unique blend of power and speed. A batter must have enough power to hit the ball deep into the outfield, but also enough speed to round the basepath faster than the outfielder is able to throw the ball back into the infield.
Home Runs |HR|
Home runs go by many nicknames (“homers”, “dingers”, etc.) but statistically, they represent hits in which the batter rounds all of the bases at once. A batter hitting the ball outside of the field of play (i.e. over the outfield wall) in fair territory represents most home runs, but there are also instances of “inside-the-park home runs”. In these cases, the ball does not leave the field of play but due to defensive misplays or the batter’s speed, they are able to score. One of the quickest ways to indicate a batter’s power, more home runs hit generally correlates with stronger, more powerful batters.
Doubles, triples, and home runs as a group are frequently referred to as “Extra-base hits”. While this is not normally denominated as its own statistic, taking the group together is another way to evaluate a batter’s power.
Batting Average |BA or AVG|
A hitter’s batting average is one of the most common ways to evaluate a player’s ability. By taking the total number of hits and dividing by the total number of at-bats over a given interval, the equation producing batting average appears as:
A 3-digit decimal, such as “0.246” represents the average, more frequently without the leading 0, i.e. “.246”. This is read as “two-forty-six”. Generally, the league-wide batting average over any interval of time falls between .260 and .275, meaning batting averages above or below this range are above or below average, respectively.
On-Base Percentage |OBP|
On-Base Percentage is a similar statistic to batting average, but instead calculates how often a batter reaches base by including walks and hit-by-pitches with hits. The equation calculating OBP appears as:
Expressed and read as batting averages are, OBP is generally a little larger than the batting average. The league-wide average OBP over a given time frame is generally somewhere around .320. It should be noted that while it is called “on-base percentage” it is not actually expressed as a percent, but rather an average.
Sabermetrics regards OBP as a better indicator of a batter’s ability as it more fully accounts for a player’s ability to affect his team’s chance to score runs. The argument rests on the fact that runs are scored due to runners rounding the basepath and that how they first reached base does not matter. That is, a run scored from a batter who walked versus a batter that got a hit is not “worth” more or less, it is worth one run no matter what. Considering how often a batter reaches base is better than how often he reaches base due to a hit.
Slugging Percentage |SLG|
Calculated similarly to OBP, slugging percentage indicates how many bases a batter earns per hit. Determined by adding a batter’s total bases and dividing by their total at-bats, this is displayed as:
League-wide average SLG generally varies between .400 and .420. Again as we said for OBP, slugging percentage is not actually expressed as a percent.
Sabermetrics regards SLG as a better indicator of a batter’s ability than AVG because it attempts to value extra-base hits differently from the more common singles. This remedies batting average’s treatment of all hits equally, even though extra-base hits have more capability of contributing to runs.
From the batting side, the concept of OBP and SLG in conjunction forms the basis of sabermetrics. Understanding these two statistics specifically is crucial to understanding the advanced statistics examined later.
Runs are a tally of how many times the batter has crossed the plate to score a run for his team. Frequently, runners who 1) bat higher in the batting order, 2) have higher OBPs, and/or 3) are fast, score the most runs.
Statistically, runs do not tell us much about the player’s individual ability. Mostly dependent on game conditions (batter, outs, position on the basepath, etc.), runs do not represent what the player himself contributed to the situation in which he scored.
Runs Batted In |RBI|
RBIs indicate how many runners a batter scores with his hits, including himself in the case of home runs. For example, if a runner is at second base, and the batter hits a single in which the runner scores, the batter is awarded an RBI. If the batter were to hit a home run instead of a double, they both would score, and the batter would be awarded two RBIs. The batters that generate the most RBIs generally 1) hit in the batting order behind high OBP batters 2) are more powerful.
RBIs, while a descriptive statistic, prone themselves to bias due to the random variations of runners being on base during a PA. As such, the sabermetric community considers this to be a poor metric for judging a batter’s ability because the main factor of earning RBIs is out of the batter’s control.
Sacrifice Fly |SF|
A sacrifice fly occurs if a batter bats the ball in the air to the outfield for an out and a runner on base advances home after the catch is made. This always occurs with less than two outs in the inning and frequently occurs with the runner on third base. It should be noted that this will also award the batter with an RBI, but will not award the batter an AB.
Sacrifice Hit |SH|
A sacrifice hit (usually called a sacrifice) occurs when a batter “bunts” the ball in the infield into a deliberate out with the successful intent of advancing a base runner. Sacrifices always occur with less than two outs in the inning and frequently occur when the team’s pitcher is at the plate. Sacrifices, like SF, do not count as an AB.
Stolen Bases |SB|
After reaching base safely, a batter (who is now a runner) may earn a stolen base by advancing on the basepath without the ball being put into play during pitches in the ensuing plate appearances of the inning. Normally, this happens by way of the runner taking a “lead” off of the base while the pitcher is preparing to pitch, and then running on the “jump” which occurs while the pitcher is in the wind-up. While the batter is running, the catcher prepares to throw the ball to the base the runner is attempting to steal. If the batter does not put the ball in play, then the runner successfully steals the base if pitching team is not able to tag the runner out before he reaches the next base.
Stealing bases is generally thought of as a display of the runner’s speed. It can also indicate a runner’s alertness to the lack of attention a pitching team may be giving him. Second base is the most common to steal, as it is furthest away from the catcher, and thus presents the highest degree of difficulty for the pitching team to defend.
Caught Stealing |CS|
A caught stealing is the converse statistic to the stolen base. A runner earns a caught stealing each time he is ruled out in the attempt to steal a base. Generally, a runner is thought to be a good base-stealer if he successfully steals around 3 out of every 4 (75%) steals attempted.
Taking a Lead: Sabermetric Hitting Stats
With this knowledge, an understanding of the game, and the Basic Pitcher Statistics, begin investigating the Advanced Hitter Statistics. Learning the finer points of advanced statistics will enable a greater enjoyment of the game. Advanced statistics allow to better recognize individual performances that are having the greatest effect on a team’s results. This allows for increased ability in evaluating a player’s performance, discussing the effectiveness of managerial choices and front office competence, and predicting the actions of a team both in-game and off the field. Many teams now rely on metrics the same or similar to those presented on this site in making their decisions.