In the process of trying to say everything that can be said about the Crisp trade, I'm afraid we've hit a problem. A big problem. Is Crisp really better than Teahen? I know we all think so, but can we twist up some numbers that will look definitive on the subject? If anyone would want to invest time into this, it would be someone here at RR.
The problem stems from three premises:
(1): A player's value is equal to a sum of his offensive and defensive contributions
(2): Teahen and Crisp are roughly equally valuable offensively--perhaps a slight edge to Teahen
(3): The best defensive stats out there (none are great) peg both Teahen and Crisp as slighly better than league average defensively at their respective positions
So if we look at just that, we're pretty much forced to say that Crisp isn't an improvement over Teahen. And we feel cantankerous. But then we remember! Crisp plays center field while Teahen plays right field! And we all know center field is a more premium defensive position!
So we rejoice, and we exclaim, "Yes, they two are even, but Crisp is More Premium!" But then we remember that we wanted a number, and "More Premium" is better suited to meats than cereals.
So now we ask, "How much is average center field defense worth? How much is average right field defense worth?" I know people have asked these questions before. Tom Tango came up with a system of positional adjustments to get at the relative values between positions. I've seen his system used by a few analysts lately, but I'm not a fan. He comes up with his values by looking at how a player's performance relative to the average changes when that player switches positions. For example, if DDJ is 5 plays below the average defense in center field, but 10 plays better than the average defense in left field, this might indicate that the average defense in center field is 15 plays better than the average defense in left field. I don't like it--who's to say DDJ isn't better suited to left? Maybe Maier doesn't call him off flyballs between them because DDJ is also a proven center fielder? I don't like the idea of taking data points exclusively from tweener outfielders who play both CF and R/LF, and generalizing the conclusions derived from that data to the broader population of all centerfielders and left and right fielders.
So those adjustments don't work for me. I don't want say Coco Crisp's defense in CF is X runs more valuable than Mark Teahen's defense in RF because David DeJesus is X runs better in left field than he is in center field. I want something that says Coco Crisp's defense is worth Y runs because if you brought in some AAA CF, he'd surrender Y more runs than Crisp would. We need to know Crisp and Teahen's values over replacement defenders.
Value over replacement player is pretty easy--as far as I know, they just take the league average, and multiply it by about 80%, and bam! that's what Jason Smith can offer you. But defense doesn't seem to be like that. A AAA center fielder won't catch 20% fewer fly balls than Crisp will. Garth Brooks would do better than that. So how is a replacement defender defined? VORP assumes league average defense for the position. Perhaps VORD should assume league average offense for that position? Something tells me our RF replacement defenders who can play league average offense for RF are already in the Majors playing 1B. So how do you define a replacement defender?