To take Burnett's place on the roster, the Pirates recalled left-handed pitcher Bobby LaFromboise from Triple A.
The 38-year-old Burnett is 8–5 with a 3.06 ERA and a 1.337 WHIP in 21 starts this season. He has struck out 114 batters and given up a National League-leading 145 hits in 135 1/3 innings.
Burnett tied for the MLB lead in games started last season with 34.
Earlier Friday, Pittsburgh acquired left-handed pitcher J.A. Happ from the Seattle Mariners in exchange for minor league pitcher Adrian Sampson. The Pirates also acquired first baseman Michael Morse and cash for outfielder Jose Tabata in a deal with the Los Angeles Dodgers.
The Pirates (59–42) play the Reds in Cincinnati on Friday.
- Molly Geary