Contreras was removed from Friday's game against the Dodgers after getting hit on the head by a pitch, Tim Healey of The Boston Globe reports.
Contreras ran for himself after getting hit by a 95-mph fastball in the third inning, but he was replaced at first base when the Red Sox went back on defense. He'll presumably be evaluated for a concussion, and the Red Sox should provide more information on his status in the near future. In the meantime, Nick Sogard will act as Boston's first baseman.