Baseball Statistics Glossary

BASEBALL STATISTICS GLOSSARY

Ever watched an MLB game and wondered, “What does that stat mean?!” We’ve put together a list for you and yours to refer to when you have those moments!

This listing will not be a comprehensive list of all MLB statistics, as that would be a 300-400 page book to read just to explain all the statistical terms you see in major league baseball and fantasy baseball, let alone when you start adding in more modern sabermetric terms.

We’ll take some of the most common terms that you will want to know to understand and enjoy the game and break them down with a basic definition that allows you to understand and/or explain the term to friends and family who may be confused. We will also divide this up into three sections – hitting/offense, pitching, and fielding/defense. Let’s start with hitting.

Hitting

Basic Terms and Information

• At Bat (AB) – A plate appearance that doesn’t end in a sacrifice, walk, or hit by pitch.
• Batting Average (BA or AVG) – Hits divided by at bats.
• Double (2B) – A two-base hit. Commonly nicknamed a two-bagger.
• Hit (H) – A ball put in play in fair territory with no out recorded that a fielder would not have “normally” have been expected to catch.
• Home Run (HR) – A four-base hit. Lots of nicknames for the home run, including homer, tater, round tripper, bomb, and many others.
• Plate Appearance (PA) – Any time a player completes a time to the plate. Used in certain percentage calculations.
• Run (R) – When a player scores a run.
• Runs Batted In (RBI) – When a batter does something that causes a run to score, other than by error, he is awarded a run batted in.
• Stolen Base (SB) – When a runner goes from one base to another during a pitch.
• Triple (3B) – A three-base hit. Commonly nicknamed a three-bagger.

More Advanced Stuff

• Batting Average On Balls In Play (BABIP) – The batting average that a batter has when he puts the ball into play. League average is typically around .300. Batters can typically “control” theirs with their batting style. Drastic above normal numbers or below normal numbers can indicate a regression to the mean coming in following season(s).
• On Base Percentage (OBP) – The times a batter has been on base, calculated by walks plus hits plus hit-by-pitch, then dividing that by at bats plus walks plus hit-by-pitch plus sacrifice flies.
• On Base Plus Slugging (OPS) – A combination measure of adding on base percentage and slugging percentage together as a measure of total offensive contribution.
• Slugging Percentage (SLG) – A measure of the amount of bases that each hit a player gets. Rather than using hits like batting average, it takes total bases divided by at bats.

A Few Sabermetric Terms To Know

• Exit Velocity – Similar to launch angle, this is information that became public after the 2015 season for the first time. It is the measure of the speed of the ball leaving the bat after contact. Higher velocities are better, but it’s combined with launch angle that they find the best exit velocity for home runs in combination with the ideal launch angle is 100-110 MPH.
• Launch Angle – The angle that a ball leaves the bat. Too shallow, and the ball is always a ground ball. Too high, and it’s a pop up. Per research from 2015 data, the best angle for a home run is roughly 20-30 degrees, though on average, Kris Bryant led the majors last year with just over a 19-degree average launch angle.
• On Base Plus Slugging Plus(OPS+) – A weighted statistic for OPS by comparing the OPS of every hitter in a particular stadium and how an individual hitter performs in comparison. The score is 100 for exactly league average, and above 100 indicates better than league average, below 100 indicates worse than league average.
• Runs Created (RC) – A statistic to estimate the number of runs that a hitter contributes to his team. There are multiple ways to compute this, much like wins above replacement (WAR), so watch the scoring, but the original formula from Bill James was walks plus hits, then taking that number times total bases, then dividing that amount by the sum of at bats plus walks.
• Weighted Runs Created (wRC) – Statistic utilizing weighted on base average (wOBA, utilized to attempt to quantify the contribution that each hit plays rather than weighing each kind of hit or walk equally) and finding how that compares to the league overall. The more prominent statistic is wRC+, which is a league- and park-adjusted version of this statistic.
• Wins Above Replacement (WAR) – A number that attempts to place a value on the number of wins that a player provides his team above the replacement-level player in the league. There are seemingly different formulas for each different WAR. Baseball Prospectus was the first to really address the statistic, and their version is called WARP (wins above replacement player). Fangraphs and Baseball-Reference each add in their own formulas, and when sourced in writing, you often see them abbreviated as fWAR for Fangraphs WAR and bWAR for Baseball-Reference’s WAR. The major differences in the calculations have to do with how each uses defense, whether a simple positional adjustment, using a metric measuring range against the rest of the league, or using something like defensive runs saved to weigh as the defensive factor in the calculation. Our Indians blog, Wahoos On First, did a quick and dirty WAR calculator if you’d like to play with how different statistics can affect the number.
• Win Probability Added (WPA) – Statistic that attempts to measure the “story” of the game by weighing the game situation when a hit happens to give it extra weight.

Next: Pitching Terms

Pitching

Basic Terms and Information

• Earned Run Average (ERA) – The “earned runs” (runs that were scored without an error allowing them to happen) a pitcher allows per 9 innings pitched.
• Hold (H) – Middle relief statistic for a pitcher who comes into the game in a save situation and turns the game over to another reliever without the game having been tied during his time on the mound.
• Save (S or Sv) – Statistic for when a reliever comes in to finish out the game and preserve a win. In the modern bullpen, this is typically done by a closer pitching the 9th inning. The game must be within 3 runs for a save to be awarded, however there can be exceptions awarded if a pitcher finishes the game by pitching 3 or more innings in relief and does not receive the win in the game.
• Strikeout (SO or K) – When the pitcher achieves 3 strikes on a batter to record an out. Often times utilized as a rate stat, either by strikeouts per 9 innings pitched (K/9) or percentage of batters faced struck out (K%). League average K/9 for starters in 2015 was 7.4 K/9 and average K% in 2015 was 19.5%.
• Walk (BB) – When the pitcher throws 4 balls to the hitter to allow the hitter to be awarded first base. Rate stats for walks for starting pitchers in 2015 averaged at 2.72 BB/9 and 7.1 BB%.
• Walks plus Hits per Inning Pitched (WHIP) – Spelled out in the name, adding walks and hits and dividing them by innings pitched for a pitcher.
• Win (W) – Awarded to the pitcher who was on the mound last for the winning team when they scored the deciding run of the game. Starters must complete 5 innings to be awarded a win.

More Advanced Stuff

• Command – The ability for a pitcher to put the ball where his catcher wants the ball, or where he wants the ball to go.
• Control – The ability for a pitcher to put the pitch near or in the strike zone consistently. It can be very important to note difference between control and command with a pitcher when reviewing walk rates for predictability.
• Earned Run Average Plus (ERA+) – A weighted statistic for ERA comparing a pitcher against the average pitcher in the league in the same environments. A score of 100 is right on league average, over 100 is better than league average, and under is worse than average.
• Fielding Independent Pitching (FIP) – A statistic that attempts to normalize the “typical” behavior for all types of hits and measure a pitcher’s performance against those metrics to give a number similar to ERA that shows how many runs he should have allowed if all fielding (and luck) in the league were equal.
• Quality Start (QS) – Statistic that measures a start by the starter’s ability to complete six innings while allowing 3 or less earned runs. Due to the volatility of the win statistic (one could get a win while giving up 10 runs if his team scored 11 runs behind him), many fantasy leagues have begun to utilize quality starts instead of wins as a statistic.

A Few Sabermetric Terms To Know

• Expected Fielding Independent Pitching (xFIP) – Taking FIP to another level, xFIP attempts to normalize home run rate for pitchers as well as the fielding behind him by using league average home run rates on fly ball rates rather than home runs for a pitcher’s home run numbers in the calculation.
• Game Score (GS) – A statistic originated by the innovative Bill James, game score measures the production of the starter. Computed by assigning scores to innings pitched, runs allowed, walks and hits allowed, and strikeouts. Average is 50, and maximum possible score with no baserunners is 114 if a pitcher went all 9 innings with no hits or walks allowed, striking out all 27 hitters. The highest game score in the history of the game is Kerry Wood‘s 1998 20-strikeout game against the Astros.
• Pitch F/X – While teams have had this information for some time, only in the last couple years have fans been able to review full data on velocity, pitch type, and movement of each pitch in the system that the league calls Pitch F/X. Data on every pitch and trends on each pitch can allow the average fan to see changes that can possibly predict performance going forward.
• Wins Above Replacement (WAR) – While this was mentioned in the hitting area, it is a different beast for pitchers. Calculating those wins above replacement utilizes different measurements for pitchers – one system will use FIP, another will use xFIP, yet another will use another proprietary pitching statistic to plug into their value metric. In general, the best pitchers are not going to grade out as well as the best hitters in Fangraphs’ version, but in Baseball-Reference and Baseball Prospectus they tend to end up fairly even.

Next: Fielding Terms