The 37-year-old right-hander underwent surgery in July to relieve nerve compression that resulted in numbness on much of the right side of his body in July, with the hope he could return for spring training. He upped the ante Tuesday, four days after working two innings in Washington.
"It was a good day," Carpenter said. "Hopefully the next few days I'll recover nicely and we'll do it again."
Cardinals manager Mike Matheny was enthusiastic, too.
"The ball was jumping out of his hand. It's really in his finish," Matheny said. "He has sink, he has cut, which he wasn't really able to do before."
Still, Matheny is trying his best to keep expectations realistic for a pitcher sidelined since spring training. Several times he sidestepped questions, and grew increasingly annoyed, when asked when the 2005 NL Cy Young winner might be ready or how he would be used -- or even if he would be used in the postseason without throwing in the regular season.
"I don't know how to make it any clearer," Matheny said. "We're taking today, and I'm not counting on him to do anything except come back tomorrow and tell us how he felt.
"My philosophy is to just let the guy go pitch, and it'll work itself out in time. I'd like to say I apologize but that wouldn't be sincere."
Cardinals general manager John Mozeliak said Monday that if Carpenter returns, it will be as a starter.
"I want to be able to pitch," Carpenter said. "I also need to make sure I'm good enough to help this ballclub. We've got some quality guys. I've got to get my stuff right, get my command right, get my pitch limit up to where I can give us a positive effort."
Carpenter said the plan calls for bullpen sessions Friday and Monday as he continues to build strength. He could replace either rookie Joe Kelly, 5-6 with a 3.34 ERA, or lefty Jaime Garcia, 3-6 with a 4.52 ERA entering Tuesday's start against the Mets, in the rotation.
After the operation in Dallas, the hope was that Carpenter could return in time for spring training. Carpenter gave himself the best chance by staying in shape before surgery.
"Coming out of it, we knew it was a shot if I could get strong," Carpenter said. "I went into it strong and I came out of it strong, so I was ahead of the game to begin with, and my arm came back nicely.
"We're moving in the right direction."
The Cardinals added another arm for their playoff drive, purchasing the contract of top pitching prospect Shelby Miller from Triple-A Memphis. The 21-year-old Miller was the Cardinals' first-round pick in 2009 and had a big August, going 5-1 with a 2.89 ERA in six starts, after inconsistent performances much of the year.
Miller's regular day in the Memphis rotation would be Wednesday, but he was available in the Cardinals' bullpen on Tuesday night.
"We brought him here to use him," Matheny said. "It's not just a gift trip. He pitched very well and he's one of the best arms we have in the system. We're in a push here, so we need to have our best ready."
Matheny said in addition to pitching well lately, Miller has matured.
Miller said the only time he has thrown out of the bullpen was in a pair of Futures Games.
"I guess I'll grab a ball, start getting hot, and they'll put me in," Miller said. "I think I'll get a good idea once it actually happens and once I'm in there."
Miller had been hoping to get the call to the majors.
"Even if you don't start too hot, good things can still happen," Miller said. "I tried to keep a positive look at it all year, and I'm here."
St. Louis also recalled outfielder Adron Chambers and infielder Ryan Jackson from Memphis. The 25-year-old Chambers has played in 23 games for the Cardinals, batting .250 in 36 at-bats. The 24-year-old Jackson played in seven games last month in his first big-league action.
Cardinals outfielder Carlos Beltran missed his second straight start because of soreness in his left knee, but Matheny said he was close to returning.