Upon further review, Bay's D not so bad?

April, 30, 2010
4/30/10
2:08
PM ET
Geoff Baker on the (apparent) rehabilitation of Jason Bay's defensive reputation:
But even more interesting than that information is the recent development on FanGraphs regarding how Ultimate Zone Rating (UZR) scored Bay's defense. We told you back in December that the Mariners had made their own, backroom inquiries about Bay's defense with Red Sox personnel and were told that it was better than he was getting credit for. Remember, there are plenty of people in this industry who maintain friendships with employees of competing clubs -- they may not have all been "competing" against one another in the past -- so these types of inquiries are actually quite common.

Flying in the face of that info, however, was the fact that Bay was getting scored by UZR, and some other defensive systems, at a below average rate. In fact, he was scored at a below average minus-13.8 by UZR last season.

So, what happened?

Well, Fenway Park happened. UZR, as we told you in a feature article last spring, in which we interviewed the system's creator, Mitchell Lichtman, uses some calculations for "park factors" but when it came to Fenway, it was more a stab in the dark. Well, now, Lichtman has introduced changes to how those park factors are calculated, and guess what?

Bay is now listed at +1.9 in his UZR defensive score for last year. He's considered an average defender based on last year's stats. Not only that, he moves up to being a 5.0 wins above replacment (WAR) player.

--snip--

In fairness to UZR, the changes made have impacted only a tiny percentage of players. Bay was among the biggest beneficiaries of the changes, so he stands out. But you have to remember, his UZR score had an enormous impact on how the debate was framed last winter as to whether or not he should be signed. In fact, it's still framing the debate today, even with the new information that says Bay was a 5.0 WAR player last season. Point of information: in Milton Bradley's career-best season in 2008, he was a 4.7 WAR player.

These defensive stats are still better than looking at only errors and fielding percentage. They are trying to measure stuff we can't see with our naked eyes. Trying to measure stuff that happens when a player does not touch a ball. It isn't easy and it's great information to have.

But it is not all that goes into grading a player. The Mariners did their homework last winter and were satisfied that Bay was an adequate defender. Not a below average one. They were not shocked by the Bay-UZR developments of the past week. Neither were the Mets, who took tons of heat last winter over the signing. I still don't think I'd have gone five years on Bay. But hey, it's their money, not mine.

As Baker points out elsewhere, one preferred method is to look at three years of UZR rather than one ... and if you look at three years -- or four years, or five -- Bay doesn't look average, or even adequate. His UZR/150 games, 2005-2009: -11.1, +2.2, -18.5, -18.3, +1.8. His career mark in left field is -8.1, which I suppose falls somewhere between adequate and awful.

I'm sure I wrote some intemperate things about Bay's defense this winter, because of his execrable UZR. I don't know, maybe I was smart enough to couch my opinion with a bit of uncertainty, because I know that weird ballparks like Fenway can gum up the works. But I believe my skepticism about Bay -- and ultimately my mild criticism of the Mets -- was influenced less by Bay's UZR and more by the Red Sox's apparent reluctance to invest a huge amount of money in him.

Because in the end, about the only thing I trust more than Mickey Lichtman and his methods is the collection of brilliant people who run the Red Sox.

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