JUPITER, Fla. (AP) – The St. Louis Cardinals have learned to not get overly excited about Chris Carpenter.

The Cardinals are 69-27 the last five seasons with their staff ace pitching. The 2005 NL Cy Young winner is 51-20 with a 3.11 ERA, and his .718 winning percentage is the best in baseball during that time. But the challenge has been getting him on the mound, with the last two seasons bringing only heartache, or more specifically, elbow ache.

The Cardinals and Carpenter were cautiously optimistic about his spotless spring training – eight scoreless innings over three appearances. Just in case, they’re conditioning Kyle McClellan as a potential replacement starter.

“I’m not going to get carried away with it,” pitching coach Dave Duncan said after Carpenter threw four shutout innings against the Boston Red Sox with only 48 pitches on Thursday. “Each time he does something that you consider a step forward and he does it successfully it’s a plus. So far, it’s encouraging.”

It’s understandable that the Cardinals are skittish about counting on Carpenter, who started on opening day 2007 but not again before undergoing reconstructive elbow surgery that July.

He returned in July 2008 intent on bolstering the rotation, but ended up throwing only 15 1-3 innings before getting shut down again, having arthroscopic shoulder surgery in September and then an operation in November to relieve irritation in his elbow.

Carpenter has been able to put that all behind him and focus on pitching this spring.

“Results-wise, it’s obviously been pretty good,” he said. “I feel like each time out there I’m getting back to game situations and trying to execute pitches.

“It’s gone the way I’d hoped. So far.”

One positive sign is how in two of his first three outings he flicked aside initial adversity.

The Mets wasted a leadoff double in the first inning of Carpenter’s spring debut and the Red Sox couldn’t capitalize on Josh Reddick’s triple on Carpenter’s second pitch of the game on Thursday.

Carpenter said he wasn’t worried about giving up a run, just executing.

“No matter if it’s here or the regular season, you can’t try to do anything more than make pitches when you get in situations like that, and that’s what I did,” he said. “If I start to concern myself with him, I stop concerning myself with making pitches, and then you get into big trouble.”

Carpenter has been building up his pitch count slowly and is behind the rest of the rotation. For that reason he won’t start the season-opener in three weeks, and is instead penciled in to pitch the fourth game of the season to keep him on schedule.

Duncan said Carpenter’s mechanics are coming along, noting he made adjustments whenever necessary.

“After being out of competition as long as he’s been, you want to let him ease back in,” Duncan said. “He’ll still have plenty of time to get his pitch count where we would like to have it at the start of the season, if he continues on like he has.”

Once again, that uncertainty. Also the reason Adam Wainwright gets the ball on opening day.

Duncan said the Cardinals began training camp with no expectations.

“Now, if you ask me what I was hoping would happen, so far this is it,” Duncan said. “But you don’t know what’s going to happen.”