Mejia (biceps) will begin a rehab assignment Wednesday with Triple-A Rochester.
Mejia reported no issues with his strained left biceps while he completed a bullpen session last week, so the Twins will have him test things out against hitters in his first game appearance since Aug. 8. The rookie will undoubtedly face some sort of pitch count Wednesday, so he could need an additional start in the minors before returning from the 10-day disabled list in September. Once Mejia is activated, he'll most likely replace Dillon Gee in the Twins' rotation.