Several times over the last year, I've tried to explore the details of Ultimate Zone Rating(UZR), a defensive metric, in part because I thought it was unfairly rating Twins outfielders. It started back in October, but if you click back, make sure you make it down to the second comment. It was by Parker Hageman of OverTheBaggy.Blogspot.com, whose research suggested that maybe UZR is biased against smaller outfields.
That's because we thought the zones in UZR didn't take into account the particular ballpark they were in. So a 350 ft fly ball down the right field line was judged similarly in park after park - even if that fly ball was a home run in the Metrodome or Target Field, but not in another field. So, somewhat ironically, the larger, more spacious outfields pumped up UZRs because fielders had more chances to make plays, while the smaller ones penalized UZR.
But we were wrong. I'm sorry UZR, I should not have doubted you.
It is apparent I was wrong because FanGraphs.com has now added a "Split" option to their statistics, including UZR. Here is Cuddyer's for last year. Instead of having the Metrodome hurt him, it helped him. Cuddyer's UZR/150 was just -6.6 at home but -22.2 on the road. All in all he cost the team just 2.7 runs at home and 7.3 runs on the road.
The same thing happens as you look at his statistics year to year, and you also see the same thing in other ballparks, like Fenway's left field. Jason Bay's 2009 season shows him having a better UZR in Fenway than on the road. So it appears that somehow, UZR is making the appropriate call for smaller outfields.
There are other weaknesses we can pick apart, but all stats have weaknesses. UZR's method for handling somewhat extreme outfields is not one of them. In fact, it seems to be a strength.
But there is something else going on here, too, I think. Somehow, Cuddyer's defense got a lot better in 2009. This offseason I'm 99% sure it said that his UZR/150 was -22.1 in 2009, but now it's -13.6? That's not an insignificant change. In some ways, that's good news, because I think that's a lot closer to what we're really seen from Cuddyer, and demonstrates his defense hasn't hurt the Twins the way other outfielders, like Jermaine Dye, have hurt their teams.
But it's also very, very bad news, because I don't know why it changed. Was there an error before? Is there an error now? If anyone knows, I'd love to hear it.
Late addition: FanGraphs apparently updated UZR recently to accomodate for extreme ballparks, and that's why Cuddyer's UZR improved, so Parker's research did indeed hold up. So we were right, but now UZR has fixed this. Here are the details: http://www.fangraphs.com/blogs/index.php/uzr-updates/