The Glossary
K/9 (strikeouts per 9 innings): The average of how many batters a pitcher strikes out per 9 innings pitched.
RC (runs created): An estimator of how many runs a batter produces for his team, created by Bill James.
WE (win expectancy): The percent chance a particular team will win based on the score, inning, outs, runners on base, and the run environment.
LI (leverage index): A measure of how important a particular situation is in a baseball game depending on the inning, score, outs, and number of players on base, created by Tom Tango.
WPA (win probability added): WPA is the difference in win expectancy (WE) between the start of the play and the end of the play. That difference is then credited/debited to the batter and the pitcher. Over the course of the season, each players’ WPA for individual plays is added up to get his season total WPA.
BRAA (batting runs above average): BRAA is the difference in run expectancy (RE) between the start of the play and the end of the play. That difference is then credited/debited to the batter and the pitcher. Over the course of the season, each players’ BRAA for individual plays is added up to get his season total BRAA.
+WPA (win advancement): The amount of positive wins a player contributed to his team, including only the plays where he increased his team’s win expectancy.
-WPA (loss advancement): The amount of negative wins a player contributed to his team, including only the plays where he decreased his team’s win expectancy.
pLI: A player’s average LI for all game events.
phLI: A batter’s average LI in only pinch hit events.
gmLI: A pitcher’s average LI when he enters the game.
inLI: A pitcher’s average LI at the start of each inning.
exLI: A pitcher’s average LI when exiting the game.
WPA/LI (context neutral wins / game state linear weights): How many wins a player contributes to his team with the Leverage Index aspect removed, invented by Tom Tango.
Clutch: A measurement of how much better or worse a player does in high leverage situations than he would have done in a context neutral environment.
