THE BOOK--Playing The Percentages In Baseball

Wednesday, September 07, 2011

UZR bias by FB%

In the midst of an article that tried to do too much was some great nugget of research, which I will repost in its entirety:

In the Granderson article I pointed out that the teams in each league which rank highest in outfield UZR for 2011 – Boston and Arizona – also ranked #1 in their league in FB%.  This remains true.  However, this is obviously not sufficient proof of correlation, for a couple reasons.  Not only is there a high possibility of coincidence in any single example, but both the D-Backs and Red Sox feature several outfielders traditionally regarded highly by both sabremetricians and scouts.  For anybody who’s watched them consistently, it would be pretty hard to argue that the trio of Gerardo Parra, Chris Young, and Justin Upton isn’t among the best in the major leagues, no matter who’s on the mound.

So, I looked back at all teams that finished at the extremes of the flyball scale since 2003.  I do not claim that there is a perfect or, in the parlance of economics, a “strong” correlation.  That is, a team with a 35% flyball rate wouldn’t have a dramatic disadvantage in OF UZR compared to one at 38%.  There is, however, significant evidence that pitching staffs with extreme batted ball tendencies can dramatically effect their outfielders UZR numbers.  (These extremes I defined at upward of 40% at the high end and below 33% at the low end.)

Average OF UZR for FB% > 40.0: 10.1

Average OF UZR for FB% < 33.0: -10.6

Of the sixteen teams at the high end of the range, five finished #1 in their league in OF UZR.  Of the 21 teams at the low-end, only five finished with a UZR north of zero.

From these I would point to some interesting pieces of anecdotal evidence:

The 2010 Giants and their 40.7 FB% led the majors in outfield UZR by a substantial margin (40.7 to 31.6), despite the fact that they gave more than 1100 innings to Pat Burrell and Aubrey Huff, lead-footed former DHs who nonetheless somehow finished with positive UZRs for the season.

The 2007 Cubs had an exceptional 44.3 OF UZR in a season where they handed most of the innings to Alfonso Soriano, Jacque Jones, and Cliff Floyd, all of whom substantially outperformed their career numbers with some help from a Chicago staff that sent 40.6% of batted balls in their direction.

On the other side, the ’05 Cardinals, despite featuring some premier outfield talent in Jim Edmonds, Larry Walker, Reggie Sanders, and So Taguchi, finished with a -6.1 OF UZR, thanks to a pitching staff that put only 29.7% of batted balls in the air.

The difference between 30% and 40% can easily be several hundred plays, so when you consider Simon’s point about the significance of even a handful of mistakes in a few months of play, you can see what kind of advantage those extra opportunities provide.

Now, I know that MGL tries to handle the FB% bias.  The more GB a team allows, the greater share of those GB that turn into outs.  And the more FB a team allows, the greater share of those FB that turn into outs.

The author here, having only access to TEAM FB%, did a decent job of trying to find the bias.  So, I’ll put it out there for MGL to verify the claim of bias, but break it down by individual pitchers.  Do high FB% pitchers have fielders who end up with high UZR in the OF?  And, is that because they happen, by coincidence to be paired to good outfielders, or is the bias more nuanced, more pervasive than it’s being adjusted for?

Thanks to Hippeaux for that great piece of research.