CINCINNATI -- A major thorn in the Reds' side for several years, Cardinals ace Chris Carpenter isn't expected be part of the two teams' rivalry for the National League Central crown in 2013.

Carpenter, who will turn 38 in April, reported to the Cardinals last week that he was feeling symptoms of discomfort and numbness in his right shoulder and could no longer throw. It was the same issues he experienced last year, when he was shut down just weeks into Spring Training. It limited the right-hander to only three starts at the end of the 2012 regular season and three more during the postseason.

"Do I envision Carp returning? I would say it's very unlikely, so no," Cardinals general manager John Mozeliak said during a Tuesday media conference at Busch Stadium.

Although it's unexpected that Carpenter would return in 2013, he did not announce his retirement. It's believed that would mean forfeiting the $12.5 million due this season in the final year of his contract.

Reds general manager Walt Jocketty brought Carpenter to St. Louis from Toronto when he was running the baseball operations of the Cardinals.

"When I signed him with the Cardinals, we were patient with him and loyal," Jocketty said on Tuesday. "He responded with loyalty to the Cardinals. You respect that. We helped him get his career back. He was one of the fiercest competitors I've been with, and since I've been with the Reds, ever opposed. He is a great person and a great teammate."

The Cardinals without Carpenter could affect the Reds' chances to repeat as NL Central champions.

A former 21-game winner, the 2005 NL Cy Young Award winner and a three-time All-Star, Carpenter seemed to make life particularly hard for the Reds. In 24 career starts vs. the Reds, he was 14-4 with a 2.55 ERA.

Carpenter won 10 consecutive starts vs. Cincinnati from Aug. 15, 2006 to Sept. 5, 2010.

Besides being a dominant pitcher, Carpenter was also at the center of some bad blood between Cincinnati and St. Louis. As a 2010 bench-clearing incident between Reds second baseman Brandon Phillips and Cardinals catcher Yadier Molina was simmering down, Carpenter rekindled the melee with words towards manager Dusty Baker and scuffled with ex-teammate and friend Scott Rolen.

On a couple of occasions in 2009 and '10 after starts at Great American Ball Park, Carpenter complained openly about the Reds giving him baseballs that were too slick because they were not rubbed down properly.

The Cardinals, winners of the 2006 and 2011 World Series, are expected to again be the Reds' primary challenger for the NL Central. Besides Carpenter, the St. Louis rotation likely includes former 20-game winner Adam Wainwright, tough lefty Jaime Garcia and top prospect Shelby Miller. The Cardinals could now look toward bringing back Kyle Lohse, who still remains on the market as a free agent.

"It's hard to tell how it will affect them," Jocketty said. "Wainwright will be better another year away from [Tommy John] surgery. It's a good rotation, as is. They have some younger guys that could be able to step up.

But no matter how the Cardinals respond after Tuesday's news, any rivalry between them and the Reds won't be the same without Carpenter.

"It's tough for the Cardinals, but I'm sure they will bounce back," Jocketty said. "You hate to see this end Chris' career, if that is what has happened. He was one of my favorite players."