Mullins had been out since late May because of a right groin strain. He was penciled into the starting lineup for Saturday, batting leadoff and playing center field.
Mullins was hitting .263 with eight home runs, 39 RBIs and 13 steals when he went down with the injury. Despite being without him for more than three weeks, the Orioles still have the third-best record in the American League. Baltimore picked up veteran outfielder Aaron Hicks, who has played well since joining the team.