Chris Carpenter’s comeback gained speed Monday night.

The veteran ace is now on the clock.

Carpenter, who has missed all season working to return from shoulder and back ailments, began his rehab trek back to the majors with 22/3 innings for Class AA Springfield (Mo.). Carpenter struck out five and allowed six hits, including one home run. He started strong with a scoreless inning that included two strikeouts and one broken-bat single. A Cardinals official at the game said Carpenter’s fastball hit 94 mph on a stadium gun.

“The velocity was good. Command can always get better, but that will happen with time, too,” Carpenter told reporters in Springfield. “Wish I could have gone a little longer, but it was fun to get out there. First live game action in a long time and looking to build off of it.”

Pitchers are permitted 30 days on a rehab assignment, and that would allow Carpenter to get at least five starts before the Cardinals have to place him on the active roster in the majors or put him back on the disabled list. The Cardinals plan for Carpenter to start again four days from now if he recovers well today from his outing.

The veteran’s pace has picked up recently, and he’s already ahead of a preliminary schedule the Cardinals had for him coming out of the All-Star break. The Cardinals planned to start Carpenter at the team’s spring training facility in Jupiter, Fla., where he could face hitters in simulated games before starting his rehab assignment. Based on how he felt coming out of two recent throws at Busch Stadium, Carpenter lobbied to start at Class AA, where the competition was higher.

“He’s a variable. He’s part of it,” general manager John Mozeliak said when asked how Carpenter fit into the planning for the trade deadline and the post-break rotation. “We’re still not at a point where I think you can make that a given. But he’s part of it. Jumping to Class AA says a lot.”

Carpenter threw 54 pitches before being relieved with two outs in the third inning at Springfield’s home game. The Los Angeles Angels’ Class AA affiliate Arkansas scored three runs off Carpenter in the third inning. Two of the runs were earned. Overall. Carpenter allowed six hits and was able to get three ground balls.