On Monday I tossed off a quick link to a column by Smilin' Geoff Baker in the Seattle Times. I used it to make reference to the fact that Jason Bay's defensive skills may have been denigrated to the point where he's actually underrated in LF. Or at least not bad enough to the point where it had a major effect on his free agent value this offseason.
The column made a larger point of trying to dissect the usefulness of UZR (quick explanation here for those of you that just come here for my Bat Attack Roundups) in light of its often dramatic year-to-year swings for a player. It's a discussion I've had with Rob on occasion. Baker used Adam LaRoche as an example, I brought it up a couple weeks ago after a perusing of Jacoby Ellsbury's numbers. As Baker notes, even though park factor is accounted for in UZR it's hardly the most foolproof part of the metric. But, the more sound explanation for players having varied year to year numbers (especially when playing for the same team) is simply sample size.
With a typical outfielder getting at least twice as many plate appearances as he does defensive chances, when reading advanced stats we've all learned to trust a single season's offensive numbers to paint an accurate portrait of a player, but to factor 3 years of defensive numbers. It makes sense, but it doesn't solve the perception problem of simply looking at a guy's UZR numbers and trying to figure what kind of fielder he is right now. Common sense tells you that you can't simply average the numbers since each year will have a different number of defensive chances, and while the reality of a player that has posted a -14.2, +10, -6.9, +12.1 is that he's got average range and average arm, it doesn't look that way on the page.
So to solve the perception problem and stop dummies like me from misunderstanding/misinterpreting the meaning of UZR, I have a humble proposal. Do away with the year-to-year UZR rating of a player, and replace it with a single career number. Beginning in a player's second year the problem of small sample size will start to dissipate and on a single look you'll be able to make a quick judgement on just how much, or how little, he's able to do in the field. To account for diminishing skills with age or trouble playing in a new park, each player's career UZR can have a little up or down arrow like the Beckett Price Guides of old representing whether his number has gone up or down in his last 400 defensive chances.
I spent time last night investigating the calculation of UZR but since the last math class I took was something called "Math For Liberal Arts II" I didn't understand most of the mechanics. But I do understand the time and effort Mitchel Lichtman put into creating and revising the stat to factor in as much relevant information as possible about dudes goin' nuts in your outfield/infield. Like donning a mint condition vintage Garfield shirt on an important date, my suggestion is mostly an aesthetic one. But one that I think has some merit.