The Pirates announced that they claimed left-hander Aaron Thompson off of waivers from the Nationals and designated Wil Ledezma for assignment.
Thompson, a 2005 first rounder who turns 24 in February, posted a 5.65 ERA with 6.3 K/9 and 3.5 BB/9 in 141 2/3 innings for the Nationals' Double-A and Triple-A affiliates last year. The longtime Marlins farmhand has yet to appear in the major leagues.
The Pirates agreed to terms on a one-year deal with Ledezma last month, avoiding arbitration. The lefty, who turns 30 next month, posted a 6.86 ERA with 10.1 K/9 and 2.7 BB/9 in 19 2/3 innings for the Pirates last year.