JUPITER, Fla. -- Chris Carpenter scowled his way through his throwing session on Monday, the first time the Cardinals ace has faced hitters this year. It's not that he was getting knocked around; it's just that one particular pitch was frustrating him.

"It shouldn't be that hard," Carpenter said afterward, "to throw a changeup."

Carpenter, the 2005 National League Cy Young winner and the undisputed ace of the World Series champions, is trying to refine his change this spring. It's always been part of his arsenal, but in recent years it's become less consistent.

He's certainly done well with "only" two fastballs, a cutter and a curveball. But he misses the old change of pace, which he once rated as his best pitch other than his curve.

"When I first came up, my changeup was my second-best pitch," he said. "I had a lot of confidence in it. It was a pitch I could throw for strikes. I got a lot of outs with it. Ever since I came back from surgery, it hasn't been there."

The change has been Carpenter's fourth pitch -- or fifth, if you view his four-seam and two-seam fastball as different offerings -- since he came to St. Louis. It's not usually a major necessity.

There are times, though, when his curveball isn't as sharp as he'd like it. And when those occasions present themselves, it would be helpful to have the change as a viable option against left-handed hitters.

"It would be nice to have one more weapon," he said. "It still could be my fourth pitch. But it would give me a chance, if one day my breaking ball is not there, maybe that changeup would be a good pitch for me. It's just something that we're working on, trying to figure it out."

Carpenter threw pretty much the whole repertoire on Monday, but fully one-fourth of the 40 pitches he threw were changeups. He saw very little hard contact from a group that included prospects Rick Ankiel, Cody Haerther and Bryan Anderson. Nonetheless, his command wasn't where he wanted it to be.

Then again, you don't get to be one of the best pitchers in baseball by being easily satisfied.

"It's not really the first step, but it's a step that you take along the way," said pitching coach Dave Duncan. "Next time he goes out he'll be better. That's what you're trying to do. You're trying to get him ready."

Duncan endorses the emphasis on the changeup. He also acknowledges that it's a bit of a luxury for a guy who really doesn't need any extra help.

"I think it's a pitch that would be a real valuable pitch for him," Duncan said. "There were times when he would get it going and it was a good pitch for him. He's thrown it. He just hasn't had the feel and the command of it that he did at one time. He's just trying to get the feel back for it."

That involves a lot of different elements, from how Carpenter holds the ball to where he locates his arm.

"I'm fiddling around with different grips," he said. "I thought I found one towards the end of the year last year that felt good, and it doesn't feel so good in spring so far. It's a pitch that you just fool around with and continue to get different grips until you feel good. Try to get locked in to the right arm slot and all that other stuff."