THE BOOK--Playing The Percentages In Baseball

Friday, January 04, 2008

UZR positional adjustments

MGL was nice enough to send me the 2007 UZR.  I can’t release the details, but I can do what I do.  As I like to do, I’ll compare the UZR by positions, for the guys who play multiple positions. 

For the OF, this is no sweat, since the skill set involved in all three positions is very similar.  From 2003-07 (that’s 5 years of data), I’ve got 7523 matching games for LF/RF.  For example, take Geoff Jenkins: he has 351 games in LF and 280 in RF.  I count that as 280 “matching games” (the minimum of the two). 

Games, by the way, is basically based on number of flyballs hit to the player divided by the league average number per game.

Do this for the 300 players that played both positions.  Add it up, and you have 7523 games.  The UZR for those guys, while in LF, was +0.7 runs.  And those exact same players, while in RF, was +0.1 runs.  That is, the comparison points in LF and RF are different for the same guys.  In order for you to standout in LF more, you have to be compared against inferior players.  And that’s what we have here: the average fielding LF is 0.6 runs worse than the average fielding RF.  And that’s just in range.  (If you include the arm, we’re probably talking about a 2 run gap between LF and RF.)

When we repeat this for LF/CF, we get 5863 games.  Those players are +4.4 in LF and -5.9 in CF, per 162 games.  That’s a 10.3 run gap.  For RF/CF (4930 games): +2.1 in RF and -9.9 in CF.  That’s a 12 run gap.  We have to make one adjustment though.  CF get about 30-35% more BIP than in the corners.  Scaling the CF opportunitues down to the number of LF/RF opportunities, we get:
LF/CF: +4.4 / -4.4
RF/CF: +2.1 / -7.4

Now, the LF/CF gap is 8.8 runs, while it’s 9.5 runs for RF/CF.  From this standpoint, the RF is 0.7 runs worse than the LF.

Overall, we can say that the avg LF = avg RF which is 9 runs worse than the avg CF (when scaled to the number of opportunities of LF/RF).

I’ll be back later for the other positions…