Mejia has been diagnosed with a left biceps strain, Rhett Bollinger of MLB.com reports.
Mejia, who was placed on the 10-day DL with the injury Tuesday, lasted just three innings in his last outing before exiting in the fourth frame. It's still unclear as to the severity and expected recovery time required for the injury, though the team will likely update his status as the week goes on. Dillon Gee is a likely candidate to replace Mejia in the starting rotation.