Adam Wainwright's contract with the St. Louis Cardinals has been put on hold because it violates the maximum-cut rule, and the pitcher will have to become a free agent before the agreement can be finalized, sources told the Associated Press on Thursday.

The Cardinals announced the agreement with the 37-year-old right-hander on Oct. 11. He has finished a $97.5 million, five-year contract that paid $19.5 million annually.

Under baseball's labor contract, his guaranteed salary could not be reduced by more than 20 percent if he remains on the roster continuously. That means he would have to be guaranteed at least $15.6 million.

His new deal contains a salary less than that figure, sources told the Associated Press. The maximum-cut rule would not apply if he becomes a free agent following the World Series and then agrees to the new deal with the Cardinals.

Wainwright was 2-4 with a 4.46 ERA in eight starts this year, sidelined by hamstring and elbow injuries. He pitched four times in September.

A three-time All-Star, Wainwright is fifth on the Cardinals' career list with 148 wins and second with 1,623 strikeouts. He was the closer when the team won the World Series in 2006.

Wainwright will be entering his 15th major league season -- all with the Cardinals, tying Bob Forsch for third among pitchers in terms of longevity with the team.

He had surgery on his right elbow to remove a cartilage flap last offseason, and he missed the 2011 season after having Tommy John surgery on his pitching arm.

The Associated Press contributed to this report.