With all the talk of Jason Bay floating around, and specifically comparing him to Mike Cameron, I thought now would be a good time to discuss methods of outfielder valuation. When we talk about valuing players, we often talk about positional adjustments, which per 150 games are typically interpreted in this way:
C: +12.5 runs
Regarding the infield, this is particularly important, since different skillsets are required to defense different infield positions. Because of this, we can interpret the values of different infielders at different positions as fixed to the position they play. Even if their offensive value remains the same at a different position, their value relative to the defensive average will vary widely from position to position in completely different ways for different players, depending on what defensive skills they have. Long wingspan and quick reactions will play well at first base and third base. A strong arm will play well at third base and shortstop. First step quickness and ability to stay low to the ground will play well at shortstop and second base. The ability to take hard slides will play better at second base. Moving a quality defensive Shortstop to first base, you wouldn't likely get enough extra defensive production to make up for the difference in the baseline positional values, and the same is true vice versa.
The outfield, however, is a completely different story. In the outfield, skillsets generally translate well position to position. There really isn't anything technically different a right fielder does than a left fielder, or even from a center fielder. There are some nuances that are different, a ball hit to left or right field generally travels differently than a ball hit straight. Right fielders have longer throws to make. But neither of these things even come close to accounting for the primary aspects of defensive value for outfielders. Research done by Tom Tango using 2007 and 2008 UZR data supports this assumption. By comparing players who have played multiple outfield positions, he has determined that players switching between a corner outfield spot and center field usually gain or lose about 11 runs compared to average. This suggests that the average defensive corner outfielder is worth roughly 11 runs less than the average defensive center fielder, and further that moving a center fielder to a corner spot, his UZR numbers would be expected to increase by about 11 runs over a full season. This 11 run mark is very similar to the 10 run difference in positional adjustments that we make when evaluating a center fielder against a corner outfielder. And what it means in most cases, except for the very extreme ones where a player's skillset would diminish his value in a different position (Think Jack Cust in centerfield), is that an outfielders total value is going to be roughly the same in a corner outfield position as compared to center field.
One of the problems with applying this conclusion to Mike Cameron is that at first glance, he seems not to fit the model. He did play one full season in a corner outfield spot, and many of us remember it well as the year Carlos Voltron usurped his center field position, where "Cammy" had been oh-so-stellar through most of his career. His UZR in right field actually decreased from the marks he'd been putting up prior, and his career UZR/150 is lower in right field than in center field. There are some problems with this type of analysis though. First, there is no UZR data prior to 2002, Cameron's age 29 season. Intuitively, adding this hypothetical "missing data" you might say that it would probably bring his career UZR/150 in center field up, only enhancing the separation. But if we assume that prior to 2002 Cameron had been an elite center fielder, in line with much of the UZR data we have as well as his reputation, it does look like there's an actual drop-off in his production right before 2005. Rather than providing elite defense in center in 2004, he was merely decent. He had a 4.0 UZR in 135 games, which is his career low up until that point using the data available, and could have very well been his career low up until that point if there was data available prior to 2002. And then, when Cameron returned to center field after being traded away by the Mets in 2006, his UZR fell to -0.1 in 141 games, and the following year all the way to -10.2 in 150 games. Its bounced back in the two seasons since to the elite level it was at prior to 2004, but it does look like Cameron may have just gone through a sustained period of his career where his defense simply wasn't as good as its been at other times. In fact, if you tally up his UZR in the roughly 430 games he played in center field from 2004-2007, his UZR/150 mark is -2.25. While that may not be a 10 run difference from his 1.9 UZR mark from 2005 in RF, it is much more consistent looking with Tango's results than just looking at Cameron's career scope, and it also falls within the realm of a typical normal distribution swing given the sample sizes we're dealing with. In addition, -1.4 of Cameron's right field UZR mark comes from a career worst ErrR, which is at least as likely to be a small sample size aberration as a representation of an actual skill difference, if not moreso.
If the opportunity cost of signing Jason Bay is a much less expensive deal that entails a shorter commitment to Mike Cameron, signing Bay is probably a mistake. It may very well be that Cameron doesn't want to come back to New York, or would prefer to continue to play center field. But if he's willing to consider a reunion with his former New York club, its an avenue the front office must explore. If you assume his value doesn't change much between CF and RF/LF, he projects very similarly to Bay in the short term and should absolutely be an option for a team that's had such a hard time finding valuable corner outfielders over the last few years. The money saved with Cameron could be used on numerous and necessary fixes to a roster filled with holes, both in the immediate short term and down the road, when Bay is less likely to be worth the value of whatever contract he gets.