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Friday, January 08, 2010
“Taking the UZR Out Of Uzer Error”
First of all, I LOVE the headline:
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.
And yes, I have been bothered by the way single-season UZR are treated similarly as single-season batting stats. As I’ve discussed in the past, 50 batting games tells you as much as 100 fielding games (more like 80 for SS and more like 130 for corner outfielders). So, I was thinking similarly to what the author was proposing, takng my cue from the world of golf and tennis: have a running total for a period of x days. In golf and tennis, I believe they look at performance over the preceding 12 months… perhaps 24 months. So, in order to interpret the UZR numbers, to get the “uzer error” out (I LOVE that!), you can try to align the fielding stats on the same level as the batting stats.
If you have a batting line with 80 games, then show the last 160 games of UZR. If you have a batting line with 140 games, show the last 280 games of UZR, etc. This keeps everything lined up with the same level of uncertainty. And, for gosh-sakes, don’t show UZR to a single decimal place. Seeing that the uncertainty is say 5.0 runs is 1 SD, I don’t see how it makes sense to show someone with a +11.2 UZR.
Now, Fangraphs does have the lovely “last 3 years” feature. But, that doesn’t stop 95% of the errors from happening.
Anyway, this is one proposal. Others?
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