THE BOOK--Playing The Percentages In Baseball

Wednesday, April 28, 2010

Player Won-Loss Records, Part 2

Now that we’ve got our feet wet in the conversion, let’s look to see if we can come up with somethig more general.  The first thing to notice is that each player’s individual W/L record can also be expressed as wins above average.  If Greinke shows as a 12-0 pitcher, then we know he’s +6 wins above average.  Therefore, if we figure out his games slices, and we figure out his wins above average, we can express his record as wins and losses.  Therefore, while WPA gave us a logical path to an individual W/L record, we no longer have to rely on WPA.  We can use anything. 

Like WAR.  And that means we can include all our adjustments, like fielding, positions, starter/relief, etc.  We start by figuring out each player’s game slice.  Let’s for the moment presume that 57% of the game slices will go to position players and 43% to pitchers.  We can refine this number in the future, and by era.  Let’s go with it for now.

With 162 games, that means we give 92 game slices to the non-pitchers and 70 to the pitchers.  With about 162*9 innings pitched for each team, this means each pitcher is going to get about 1 game slice for every 20.8 innings pitched.  Relievers with their leverage will complicate this, but, again, let’s set that aside for now.

Baseball Projection.com has Sandy Koufax at 54.5 WAR and 2324 innings.  Ideally, we’d prefer to see it as wins above average (WAA).  Let’s say he’s 28 wins above average.  So, we have all that we need.  The 2324 innings gives us 112 game slices, putting the average pitcher at 56-56.  Koufax is +28 wins above that, or 84 wins and 28 losses.  So, that’s Koufax’s record:
84-28 Koufax

I know there’s a temptation to turn that into a percentage.  Don’t.

Pedro has 2827 innings and 76 WAR (probably +45 WAA).  That converts to 136 game slices, and a 113-23 record.  So, that’s what we have:
113-23 Pedro
84-28 Koufax

For position players, we can follow a similar process.  There’s roughly 6300 PA for each team, and 92 game slices to give out, or one game slice for every 68.5 PA.  Tim Raines had 10244 PA and 65 WAR (or about +33 WAA).  His game slice comes in at 150, and so his W/L record is 108-42
113-23 Pedro
108-42 Raines
84-28 Koufax

And that’s how a player’s individual W/L record looks like.  If we use WPA, we guarantee summable at the team-season level (indeed at the GAME level).  Using WAR or WAA means we lose that, but we gain in terms of being able to add in things like fielding and positions.  And, in any case, we’re more interested to getting something out there for a big number of players, and we can sweat the details later.