You've likely already seen that Jesse Chavez's career as a Ray ended quickly this week, as he was flipped from Tampa to Atlanta in exchange for Rafael Soriano. This has some people grumbling, because while it's sometimes hard to compare things like the upgrade Iwamura provides over Delwyn Young at second base to the hit the bullpen takes in losing Chavez, it's pretty obvious that Soriano is a better reliever than Chavez.
The set of circumstances that caused this series of trades is pretty remarkable. Ben Zobrist had a monster breakout year in Tampa, forcing the Rays to trade Iwamura for less than he was worth because the money earmarked for his salary would be better spent somewhere like their bullpen than on a utility man. In turn, the Braves went out and spent a ton of money on Billy Wagner and Takashi Saito, only to have Soriano acccept their arbitration offer and give them a bloated bullpen. In turn, they were forced to trade him for less than he was worth and the Rays, with their newly available funds and needs in the bullpen, offered up Chavez to an Atlanta team all too happy to get anything in return for their suddenly expensive problem.
In effect, the Pirates and Rays both leveraged the five years of remaining team control over Chavez to move an otherwise unremarkable reliever for a good player that should help their respective teams in 2010. The whole fascinating circle is brought together by this great FanGraphs piece by Dave Cameron on why it's not a bad idea for the Rays to pay Soriano $7 million, more than a tenth of their payroll. To build on that from the Pirates' perspective, Iwamura and Soriano are both worth about two wins over the course of a season (actually, Iwamura will be worth a little more and Soriano a little less, but stick with me), provided they're both healthy. To the Rays, though, Iwamura was slated for a backup role which, in their ideal world where Zobrist and Longoria don't get hurt, would cut his value down considerably.
Thus, even though the current going rate for a win is $4.5 million, Iwamura wasn't likely to be worth his paycheck to them. Soriano, though, fills an important need for them and because, as Cameron points out, wins are more valuable to a contender, Iwamura isn't worth $4.85 million to them, but Soriano is worth $7 million whereas Soriano wouldn't be worth to $7 million for the Pirates, but Iwamura should be at least worth his salary to the Pirates and will probably be worth a little more. So both teams end up with players they needed and both managed to do so by trading Jesse Chavez, who in turn will probably end up being valuable to the Braves simply because he should be in blue and red longer than either of the players that were traded for him will wear their new team's uniforms.
Coming full circle back to my original point, this series of trades is fascinating if for nothing but the coincidental circumstances and I think in the end, the Pirates have the player that's right for them.