Originally Posted by mth123
Some questions for the stat gurus. Is the stat accepted as valid? Does defense factor in? Does anyone have the numbers for pitchers this year?
I'm not a stat guru, but I find WPA to be very entertaining and couple of years ago I contacted Dave Studeman from the Hardball Times to see if he could process the REDS games and post the results here in REDSZONE. It worked for about two weeks, but it was too much work for Dave, so we called it off.
Here's an article he wrote in the HBT, which explains a bit more about WPA:
The stat is tossed around, but I wouldn't say it is general "accepted", because as far as I know, there hasn't been an agreement on a standard table of Win Probability per game situation.
There is historical data...that is, how many times a team has won starting from a certain situation. Tangotiger has published it here:
It's fun to see, in a certain moment of a game, how likely a comeback is.
But some situations have small sample sizes, so generally a standarized table is used. Making a standarized table involves assumptions, such as average runs per game, home field advantage (or not),park factors...etc. There is no consensus on those assumptions, so the tables will vary depending on who calculates it.
But it shouldn't vary THAT much from one source to another. This is a counting stat and the player either performed (and gained WPA) or did not (and lost WPA).
As far as I have seen the fangraph.com calculation is a very simple one. Defense is NOT factored in, as in a player will get credit when reaching on a error (which probably isn't fair). When Dave was doing the REDS games, he would distribute WPA from a non-routine play between the defense and the pitcher, to make it fairer. But this was subjective and involved much more work on his part. You could get an idea of how much defense was helping or hurting the team.
Eliminating defense may not be as "accurate" but it's objective. Player hit ball..good things happened...he gets credit. And its a LOT easier. Fangraphs.com tracks WPA IN REAL TIME in these cute little graphs which I in particular enjoy very much.
The pitchers WPA is also tracked. Its just the opposite of the hitters WPA.
As can be expected, late inning relievers can generate a lot WPA, and the stat in several forms and variation is used to track relievers peformance.
The same page that has hitter's performance has the pitcher's WPA
Volquez leads the starters and Cordero the relievers. No surprise there.
There are other interesting stats on the page, such as pLI...which shows how "leveraged" (critical) the situations for the players were.
(high for a reliever, low for a starter, high for PH hitter, for example).
enough for now...