Perez, 34, was a starter back then. He will most likely come out of the bullpen as a setup man and left-handed specialist. Perez has been a reliever the past four seasons, during which he appeared in 253 games with a 3.67 ERA and 238 strikeouts in 196 1/3 innings. Perez joins Felipe Rivero as the lefties in the Washington bullpen.
Perez is best remembered as a starter with the Pirates and Mets. His best year in that role was 2004, when he won 12 games and had a 2.98 ERA with Pittsburgh. He went 15-10 with a 3.56 ERA for New York in 2007.
He split last season -- his 13th in the Major Leagues -- between the D-backs and Astros, going a combined 2-4 with a 4.17 ERA in 41 innings over 70 appearances. He had a 3.10 ERA in 29 innings over 48 games for Arizona before being traded to Houston on Aug. 8.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the Time. He also can be found on Twitter @WashinNats. This story was not subject to the approval of Major League Baseball or its clubs.