St. Louis Cardinals pitcher Chris Carpenter will undergo shoulder surgery and will be out the rest of the season, multiple media outlets reported Tuesday.

Carpenter, who has finished among the top three in the Cy Young Award voting three times and won the award in 2005, has had nerve-related shoulder problems that flared up following his most recent bullpen session.

The operation to alleviate Carpenter's thoracic outlet syndrome was deemed necessary, whether he tried to pitch again this season or not.

Carpenter, who has not pitched for the Cardinals this season, decided to have the procedure performed now to increase his chances of pitching by next February.

A date for the surgery has not been announced.

Carpenter threw a bullpen session on Friday, and he was been scheduled to throw another bullpen session on Monday before the latter was canceled.

Carpenter, 37, is in the first year of a two-year, $21 million contract extension.