Glossary: Relievers Expected Wins Added
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Games played (pitched, fielded, officiated).
Properly speaking, a pitcher should only be credited with a game played on his batting line when he actually appears in the lineup (i.e., not when a DH hits for him.) The BP database is currently inconsistent in this respect.
Leverage measures how important the situations a reliever has been used in are. A leverage of 1.00 is the same importance as the start of a game. Leverage values below one represent situations that are less important than the start of a game (such as mopup innings in a blowout). Leverage values above one represent situations with more importance (such as a closer protecting a one-run lead with bases loaded in
the 9th inning).
Mathematically, leverage is based on the win expectancy work done by Keith Woolner in BP 2005 (read an explanation by Dan Fox here), and is defined as the change in the probability of winning the game from scoring (or allowing) one additional run in the current game situation divided by the change in probability from scoring
(or allowing) one run at the start of the game.
League. 'A' or 'AL' denotes American League. 'N' or 'NL' denotes National League.
As used in most places (including the PECOTA cards), Team is the three letter abbreviation for a major league, minor league, or foreign team.
The probability of winning the current game, given some
information about how many runs each team has scored to a certain point in the game, how many outs there are, whether there are runners on base, and the strength of each team. Keith Woolner outlined a method for computing Win Expectancy given all of these parameters in BP 2005.
Expected wins added over an average pitcher, adjusted for level of opposing hitters faced. WXL factors in the MLVr of the actual batters faced by the relievers. Then, like WX, WXL uses win expectancy calculations to assess how relievers have changed the outcome of games.
Expected wins added over a replacement level pitcher. WXR uses win expectancy calculations to assess how relievers have changed the outcome of games, similar to WX. However, instead of comparing the pitcher's performance to an average pitcher, he is compared to a replacement level pitcher to determine WXR.
Win Expectation above Replacement, Lineup-adjusted.