Contreras was removed from Wednesday's game against the White Sox with a left foot contusion, Ian Browne of MLB.com reports.
Contreras fouled a ball off his foot during his at-bat in the top of the third inning, and although he managed to finish the plate appearance, he later took himself out of the game in the bottom of the frame. His diagnosis suggests he avoided a fracture, though the Red Sox could hold him out for a game or two so he can recover. Romy Gonzalez entered Wednesday's game as Contreras' replacement and would be the favorite to start at first base during any games the latter has to miss.