The Reds added Petty to the active roster as the 27th man for Saturday's doubleheader against the Cardinals.
Petty will make his second big-league start of the season in the second game of Saturday's twin bill. He gave up three earned runs over 5.2 innings during his season debut against the Cubs on May 4 but owns a 6.32 ERA and 1.64 WHIP through 31.1 frames in Triple-A. He'll likely be sent back to Louisville following his appearance Saturday.