Stewart (hamstring) will undergo an MRI on Wednesday, Stephen J. Nesbitt of the Pittsburgh Post-Gazette reports.

EDGE Analysis

While the injury originally wasn't thought to be anything overly serious, Stewart tried testing it out prior to Tuesday's contest and failed, prompting him to hit the DL. A possible timetable for his return should become clearer following Wednesday's tests. In the meantime, Elias Diaz will serve as the Pirates' backup catcher.