Contreras was removed from Tuesday's game against the Twins due to lower-back tightness, Tim Healey of The Boston Globe reports.
Contreras was hit by a 92.7-mph sinker in the fourth inning and was eventually replaced on defense by Andruw Monasterio in the fifth. Details regarding Contreras' short-term availability should emerge after the Red Sox take a closer look at him, and if he has to miss any amount of time, Monasterio would be the favorite to receive starts at first base.