There has been much consternation in Cubland over the trade of Milton Bradley for Carlos Silva. As a Cub fan, I cannot say I was happy about the trade when it happened. J.C. actually thinks it did not hurt the Cubs too much, though that is mostly based on the combination of Silva not being completely worthless and the six million dollars. But most importantly, J.C. does not value Bradley particularly highly. Interestingly, I do not think his methodology accounts for much negative value for Bradley's attitude. Baseball Analysts estimates that that could cost his team as much as 1.5 wins above replacement, though this might be hard to look at on straight value as there is certainly an asymmetric effect. Bradley's attitude costs the Cubs more than it will cost the Mariners. The analysis from the Baseball Analysts, however, generally feels the Mariners won the trade. Presumably the difference here is from a higher estimated on-the-field value for Bradley.
An example of a bad analysis of the trade comes from Fangraphs. There are two main problems with their analysis. The first problem is the assumption that Silva will replace Gorzelanny in the rotation. First, if Gorzelanny is the much better pitcher, even the Cubs would presumably start him regardless of how much they are making. Second, Lilly is hurt, so the Cubs will have to need an additional starter. Given that Lilly was the only lefty in the rotation and that Gorzelanny is a lefty and Silva is not, that one of the spots in the rotation would be Gorzelanny's to lose. Lastly, even if the Cubs have no plans for Gorzelanny, he still has trade value and the Cubs could recoup some of his value.
The second problem is completely not accounting for the difference in defensive value because Byrd will be playing CF and Bradley would be playing RF. Their assumptions of the trade being essentially Silva and Byrd for Bradley, turned out to be correct as the Cubs used most of the money from the Mariners to sign Marlon Byrd. Pretty much any analysis of their offensive contributions will conclude that the Cubs are taking a hit to their offense. Some of the commenters at the original post suggest that a defensive position update needs to be made. However, I think that is slightly incorrect. They are essentially replacing one for the other in the lineup, so the offensive contribution is correct. However, at the same time, the Cubs have dramatically improved their defense with the move. This table summarizes the defensive issue:
Fielding Bible Zone Rating
Player value in RF value in CF value in RF value in CF
Byrd -5 0 to -9.5
Fukudome 3 -5 13.1 -18.1
Bradley -7 -6.9
Even if Byrd is not much of an upgrade over Fukudome in CF, Fukudome is a big upgrade over Bradley in RF. Regardless of whether the improvement in defense outweighs the downgrade in offense, any analysis of the trade ignoring defense is going to be insufficient.
The most distressing thing about the analysis is that it comes from a sabermetric site (and a generally good one at that).