Stats Glossary (Mostly Analytical)

[Greg Pappas]

I'm probably annoying some posters, but with my ongoing memory issues, I feel the need to create a single place to reference the numerous analytical statistics that we often use when discussing player performance.  Much of this comes from CallToThePen.

I didn't add Defensive stats as they're mostly foreign to me, but I'd appreciate any insight folks wish to share on that. I'd also be grateful if this were pinned, as I feel it would help others as well.

Hitting: Analytical Terms

• (BABIP) Batting Average on Balls In Play: 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.
• (EV) Exit Velocity: It is the measure of the speed of the ball leaving the bat after contact. Naturally, higher velocities (100+ mph) are better.
• (ISO) Isolated Power: A measure of a hitter’s raw power and is a quick tool for determining the degree to which a given hitter provides extra base hits as opposed to singles. 
• (LA) 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. The best angle for a home run is roughly 20-30 degrees.
• (OBP) On Base Percentage: 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.
• (OPS) On Base Plus Slugging: A combination measure of adding on base percentage and slugging percentage together as a measure of total offensive contribution.
• (OPS+) On Base Plus Slugging Plus: A weighted statistic for OPS by comparing the OPS of every hitter in a particular stadium and how an individual hitter performs in comparison. 100 is league average.
• (RC) Runs Created: A Bill James sabermetric statistic used to estimate the number of runs that a hitter contributes to his team. The resulting number is viewed similarly as RBI's. So, 100 is considered good for a full time player.
• (SLG) Slugging Percentage: 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.
• (WAR) Wins Above Replacement: 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.  Fangraphs and Baseball-Reference each add in their own formulas which you often see abbreviated as fWAR for Fangraphs WAR and bWAR for Baseball-Reference’s WAR. 
• (wOBA) Weighted On Base Average: This is a rate stat that attempts to credit a hitter for the value of each outcome (single, double, etc) rather than treating all hits or times on base equally.  wOBA is designed on the same scale as OBP, so .320 is typically average and .311 is currently average in 2024.
• (WPA) Win Probability Added: Statistic that attempts to measure the “story” of the game by weighing the game situation when a hit happens to give it extra weight.
• (wRC) Weighted Runs Created: An upgraded version of RC.
• (wRC+) Weighted Runs Created Plus: Fangraphs calls it the most comprehensive rate statistic used to measure hitting performance, because it considers the varying weights of each offensive action and then adjusts them for the park and league context in which they took place. It may be the single best overall player performance measurement, above even wRC, wOBA and OPS+. League average for position players is 100, and every point above 100 is a percentage point above league average. 

Pitching: A Few Standard Terms

• 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 especially important to note the difference between control and command with a pitcher when reviewing walk rates for predictability.
• (QS) Quality Start: 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.
• (WHIP) Walks plus Hits per Inning Pitched: Spelled out in the name, adding walks and hits and dividing them by innings pitched for a pitcher.

Pitching: Analytical Terms

• (ERA+) Earned Run Average Plus: 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.
• (FIP) Fielding Independent Pitching: 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.
• (WAR) Wins Above Replacement: 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.
• (xFIP) Expected Fielding Independent Pitching: 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.

Please feel free to comment.

Edited June 21 by Greg Pappas