Petersen was lifted from his relief appearance during Sunday's game against the Padres due to a right forearm contusion, Christina De Nicola of MLB.com reports.
Petersen came on in relief of starter Janson Junk with two outs in the fourth inning and threw just two pitches before he was nailed by a grounder off the bat of Ty France. Marlins catcher Joe Mack gathered the loose ball and threw to first base to record the final out of the inning, but Petersen retreated to the locker room immediately after the play and wasn't available to return for the top of the fifth. Petersen has now made early exits from two of his last five relief appearances, as he was previously lifted from a July 12 contest against the Guardians due to a hamstring injury before getting a clean bill of health coming out of the All-Star break.