Wellemeyer, who made two rehab appearances for Triple-A Memphis on Monday and Wednesday, is 7-9 with a 5.67 ERA in 23 games for the Cardinals.
"The second one was better than the first one," Wellemeyer said. "I still made good pitches in the first one, I just wanted to make sure that I was around the plate and get a good feel. I figured some stuff out yesterday. Hopefully I can help us out through the rest of September."
Kyle Lohse, on the disabled list with a strained left groin, threw a light bullpen session on Thursday and will be activated on Sunday when his time on the disabled list runs out. The Cardinals plan to use him out of the bullpen as well until a spot opens up for him to return to the rotation.
B.J. Rains is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.