Chris Carpenter threw 51 pitches during a three simulated innings against teammates at Busch Stadium on Tuesday.
Carpenter had surgery in July to alleviate nerve pain near his right shoulder and is building his pitch count with each outing in an effort to rejoin the rotation.
The Cardinals are open to using Carpenter as a starter down the stretch if he can continue to increase his pitch count.
"I've been around long enough to be able to figure out whether I'm good enough to pitch and my stuff is good enough to pitch," Carpenter said. "My stuff (Tuesday) was good. I could go out and get outs in a game with it. That's no question about that. It (isn't) determined by the level of pressure the game has. … If I come back and I'm healthy and my arm is conditioned enough to go out there and do something, I can help."