The Tigers traded Ryan Perry to the Nationals for Collin Balester
Balester had a -.3 WAR in 2011, and a -.6 WAR for his career. He has a 2.22 PE for his career, with a 2.34 Adjusted PE mostly as a reliever with 22 starts mixed in earlier in his career. His FIP - is 128 with a BABIP of .295, and he has struggled massively with homers at 1.67 HR/9IP. SIERA is a little nicer to him with a 4.28 career number, and he has slightly more groundballs than flyballs. He isn't arbitration eligible yet.
Perry had a -.4 WAR in 2011, but has a .7 career WAR. He has a .76 PE, with an adjusted PE of .97, all as a reliever. He has a career FIP - of 99, and SIERA of 4.28 (mysteriously the same as Balester's). He has done a good job avoiding the long ball, with a .78 HR/9IP. He has a higher walk rate that Balester and a very similar groundball rate. He is arbitration eligible. Perry is, according to most metrics, the better pitcher. Even though his salary will probably be higher than Balester's, I think the Nationals win this trade.