The Reds optioned Petty to Triple-A Louisville following Friday's game against the Orioles.
The move makes room on the Reds' 26-man roster for Hunter Greene (elbow), who was reinstated from the 60-day injured list ahead of his scheduled start against Baltimore on Saturday. Petty has appeared in 10 major-league games (two starts) for Cincinnati this season and has a 4.37 ERA, 1.10 WHIP, one save and a 9:7 K:BB across 22.2 innings.