Walters (lat) was charged with two runs on one hit and one walk over an inning of work in his first rehab appearance with Triple-A Columbus on Tuesday.
Walters averaged 94 mph with his four-seamer, which is down 2.4 mph from his average with the Guardians last season prior to lat surgery. The velocity could come back as he further distances himself from the operation, but if it doesn't, the Guardians might opt to keep Walters at Columbus for a while rather than stick him back in the big-league bullpen.