Jemagee, FuquaManuel and I kind of got into this a little bit on the 10/4 game thread. FM, I believe it was, said that Uggla could play 3d; I voiced concern about replacing Feliz's defense with Uggla, and was challenged to come up with some stats to substantiate my concern. They probably thought I would just go away and take my uninformed opinions with me. No such luck!
I did some digging, and I therefore present for your consideration some numbers to consider when adjudging whether Uggla could replace Feliz on defense. I'll leave offense for another FanPost, or another day.
I figured I'd get numbers for Uggla and Feliz as well as, for comparison's sake, since they play different positions, one other generally well-regarded defensive player for each of their respective positions, - Utley and Ryan Zimmerman - and I'd get stats for each of the last two seasons. I got Runs Allowed Above Average 2 (adjusted RAA) from Baseball Prospectus; Ultimate Zone Rating from FanGraphs; and Range Factor from ESPN (also available as RF/9 on Baseball Reference). I was able to find NL rankings for 2B and 3B for the latter two stats but I can't find where BP gives rankings for RAA2.
RAA2 UZR UZR rank RF RF rank
Uggla 08 4 1.6 3d of 7 4.86 6th of 7
Uggla 09 13 -12.6 11th of 11 4.44 11th of 11
Utley 08 15 20.2 1st of 7 5.18 1st of 7
Utley 09 -8 11.2 1st of 11 5.05 3rd of 11
Feliz 08 -6 7.2 1st of 11 2.72 3rd of 11
Feliz 09 25 5.8 4th of 9 2.83 3rd of 10
Zims 08 -6 2.1 7th of 11 2.91 [would be 1st]
Zims 09 10 18.9 1st of 9 2.97 2nd of 10
And this tells us............ um, I dunno, you tell me. Between 08 and 09, Uggla and Feliz both supposedly get better by RAA2, but worse by UZR. Feliz and Zimmerman are supposedly six adjusted fielding runs below average in 2008 - the same season that Feliz was in the top three in the league by both UZR and RF. Utley's numbers are consistently very good, except for being 8 adjusted fielding runs below average this year. Uggla meanwhile has generally lousy numbers except for being 13 RAA2 in 09 and 3rd out of 7 in the league by UZR in 08.
Feliz comes out as best in the league (among qualifiers) at UZR in 2008, but not so good in RAA2 that year. The next year he was 25 adjusted runs above average :) but only 4th of 9 qualifiers in UZR :(.
In terms of my discussion with Jem and FM, there's evidence here that one could point to as support for a claim that Feliz is a good defender and Uggla a bad one, and that therefore we would have to assume that, in addition to the presumed difficulties of learning a new position, Uggla would bring along his generally subpar defense, and that that Phils defense would measurably and noticeably suffer.
But the data is ambiguous enough that I think you could equally well set it all aside as conflicting and inherently unreliable. So - I've met Jem & FM's challenge to dig up some numbers. But those numbers don't consistently support my argument that the Phils' defense would measurably and noticeably suffer if we swapped out Feliz for Uggla at 3rd base.