Walters, on the disabled list since June 14 with right shoulder inflammation, was on a 35-pitch limit, but was only able to record two outs on 33 pitches before being removed from the game. He gave up two runs on four hits and a walk.
"He didn't throw the ball well last night, but came out healthy so he'll move forward," Gardenhire said. "He'll probably get up to what we hope would be 45-50 pitches next time."
In other injury news, closer Matt Capps still hasn't thrown a ball since being placed on the DL on July 17 with right rotator cuff irritation. But he continues to do rehab on his shoulder and will be re-evaluated by team doctors on Monday.
Right-hander Carl Pavano is set to make his second rehab start with Class A Fort Myers on Sunday. Pavano, on the disabled list since June 4 with right rotator cuff weakness, threw two innings in his first rehab outing on Tuesday.
Reliever Anthony Swarzak is continuing to throw long toss. He's on the DL retroactive to July 25 with a mild right rotator cuff strain.