After first lauding them, I have become disenchanted with UZR and other defensive rating systems. There is too much guesswork and too many assumptions made that go into the calculations. My biggest issue is that the numbers are based off of a zero average and fluctuate wildly from year to year. (Quick example. Omar Vizquel‘s UZRs from 2003 to 2009: 3.7, -0.7, 7.0, 9.3, 23.1, 3.0, 5.6) I don’t think his actual skill changed that much from year to year. I see it as the general quality of defensive skill of the league revolving around him.
With that background I found Colin Wyer’s article to be very refreshing. I hope more people like him keep striving to remove the biases from batted ball data.