Philadelphia infielder Michael Martinez broke a bone in his right foot when he was hit by a pitch from Orioles reliever Jim Johnson in the seventh inning of the Phillies' 4-1 win over Baltimore.
There is no immediate timetable on Martinez's return.
Philadelphia has already been without All-Star infielders Ryan Howard and Chase Utley.
Martinez, a Rule 5 pick two winters ago, was a candidate for a roster spot as an utility infielder.
''A lot worse things have happened I guess,'' Phillies manager Charlie Manuel said of losing another infielder. ''We lose somebody, we'll get somebody else. Lou Gehrig got to play, didn't he?''