ST. LOUIS – Cardinals ace Chris Carpenter had reconstructive elbow surgery Tuesday, an operation likely to sideline him for at least a year.

The 2005 NL Cy Young Award winner, out since opening day, had surgery in early May to remove bone spurs and was on a rehab assignment for Class A Palm Beach when he developed swelling and stiffness July 8.

St. Louis team physician Dr. George Paletta operated Tuesday to repair the ulnar collateral ligament in Carpenter’s right elbow.

Carpenter was 3-1 in five postseason starts last year and threw eight scoreless innings against Detroit in Game 3 of the World Series, helping the Cardinals win their first championship in 24 years. He’s 51-18 with a 3.10 ERA in 93 starts for St. Louis over the last three seasons.

Carpenter hasn’t pitched since allowing five runs in six innings during a season-opening loss to the New York Mets. He reported elbow stiffness and swelling the following day.

Cardinals left-hander Mark Mulder and right-handers Todd Wellemeyer and Josh Kinney also are on the DL. Kinney had reconstructive elbow surgery this spring.

Mulder, who had rotator cuff surgery last September, threw a bullpen session Tuesday and could be close to a rehab assignment.

“He’s making progress every time he goes out there,” manager Tony La Russa said. “It’s been exciting.”