Right-handed reliever Chris Resop, one of the seven arbitration-eligible Pirates players facing Friday's deadline to be tendered a contract, instead was dealt Friday evening to the Oakland A's.
Pittsburgh received Zach Thornton, a 24-year-old righty who spent the 2012 season in Class A, from Oakland.
In a separate transaction, the Bucs acquired another right-handed prospect, 19-year-old Jhondaniel Medina, from Baltimore in exchange for infielder Yamaico Navarro.
Resop, 30, was an instrumental member of the Pirates bullpen since being acquired on waivers from Atlanta in August 2010. In two-and-a-half seasons with the Bucs, he appeared in 159 games, posting a 3.88 ERA. He appeared in 61 games last season, compiling an ERA of 3.91.
Thornton posted 16 saves in 48 games at Stockton, and had 70 strikeouts in 53 2/3 innings. A 23rd-round Draft choice in 2010 out of the University of Oregon, Thornton has picked up 187 strikeouts in 169 2/3 innings as a professional.
The Pirates had earlier designated for assignment Navarro, whom they had acquired a year ago in a trade from Kansas City.
Medina made seven starts among his 11 appearances this season between the Orioles' Rookie and Class A farm clubs. He had a combined record of 1-3, with a 4.14 ERA and 50 strikeouts in as many innings.