Gsellman (hamstring) was officially placed on the disabled list Wednesday, Anthony DiComo of MLB.com reports.
Gsellman left Tuesday's contest after suffering a left hamstring strain in the fourth inning. The right-hander had been struggling on the mound recently, allowing 17 earned runs over his last three starts (12.1 innings). Gsellman is likely to return before the All-Star break since the injury seems to be a minor setback. In his place, the team recalled infielder Matt Reynolds and added him to the 25-man roster.