Without yet knowing the salary particulars, it's hard to know how to evaluate this one. For Sean Casey, the Bucs get Brian Rogers, just a minor league reliever, but a pretty good one. The Tigers' 11th round pick in 2003 out of Georgia Southern just turned 24. He has pitched very well as a reliever in Classes A+ and AA since converting to relief after the 2004 season.
Still, a minor league reliever is a minor league reliever. Rogers will probably eventually pitch for the Pirates, but this is probably basically a salary dump. I'm fine with that, since it seems to mean that signing Casey to an extension isn't at the top of the Pirates' list of priorities.
I wonder what Casey's role with the Tigers will be. This trade is somewhat ironic in that the Tigers' regular first baseman is Chris Shelton, who Pirates fans complain about losing all the time. Shelton is pretty unambiguously way better than Casey. Still, DH is a weak spot for the Tigers right now - Dmitri Young is fragile and he hasn't hit well since returning from injury. If I were the Tigers, I'd use Casey to soak up some at-bats as a DH and to rest Shelton against tough righties.
Whoa... the Tigers actually demoted Shelton. Wow. That's not the move I would've made. Casey isn't, you know, good and keeping Shelton on the roster wouldn't prevent the Tigers from reaching the playoffs even if he were. Shelton is younger and is clearly superior on defense and probably also on offense.
...Marc Normandin points out that Casey hasn't actually hit better than Shelton the past couple of months anyway. Weird.
...I'm having trouble finding any information on the web about Rogers. It seems that no one views him as much of a prospect at all. A couple of web sites that no longer exist suggest that he throws 87-90 MPH; if that's true (and it may not be), he could be the sort of pitcher who can dominate minor leaguers but won't improve enough to thrive as he moves up.
...This is a message board, so take it for what it's worth, but it says that Rogers' fastball is only 85-86 MPH but that he has a weird delivery that keeps batters from picking up on it.