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

Fielding

Basic Terms and Information

• Assist (A) – Any play where a fielder fields the ball and throws to a base to make an out is an assist. Context is important, however. An average starting shortstop will have 400 assists on a season while an outfielder that reaches 10+ assists in a season has had a very good defensive season in throwing runners out.
• Error (E) – Determined by the official scorer of the game, a play that is determined should have been made by the fielder but was not due to something that the fielder did.
• Fielding Percentage (FPct) – Simple statistic that measures total chances minus errors and divides that number by total changes for the percentage of “clean” plays made.
• Passed Ball (PB) – A pitch that gets by the catcher that it is deemed by the official scorer to have been due to fault of the catcher and not the wild-ness of the pitch thrown.
• Position Numbers – When reviewing defensive statistics, you will often see positions referred to by their number. An error on the third baseman won’t say “E3B”, it will say “E5”. The positions are numbered as such: 1. Pitcher, 2. Catcher, 3. First Base, 4. Second Base, 5. Third Base, 6. Shortstop, 7. Left Field, 8. Center Field, 9. Right Field

More Advanced Stuff

• Range – The amount of ground a fielder covers from his positioning when the pitch is thrown to where he makes the play on a ball put into play. Shortstops and Center Fielders are typically the infielders and outfielders expected to have the greatest range, respectively.
• Route – The path that a fielder takes from his starting position to where he fields the ball, typically most utilized in fly balls and pop ups. This is especially utilized in reviewing outfielders.

A Few Sabermetric Terms To Know

• Defensive Runs Saved (DRS) – A defensive statistic to attempt to quantify the value that a defensive player adds to his team by figuring the runs he either added to or cost his team due to his defense.
• Range Factor (RF) – Statistic that takes putouts and assists, multiplies that by 9, and divides that number by the amount of innings played at a position. You’ll see it weighted as RF/9, which is range factor per 9 innings at a position.
• Ultimate Zone Rating (UZR) – A statistic that attempts to measures what happens on a ball hit to a particular zone with an “average” fielder versus what happened with that particular fielder. Similarly to DRS, it is measured in runs saved or cost for the team. An exceptional UZR is anything over +15. This is also expressed often in UZR/150, which is UZR per 150 games.