St. Louis Cardinals pitcher Chris Carpenter underwent neurogenic thoracic outlet surgery Thursday in Dallas, Texas.
The anticipated time of rehabilitation is 2-to-3 months.
"We are pleased with today's results and Chris will soon return to St. Louis to begin his rehab," said Cardinals general manager John Mozeliak. "We look forward to seeing Chris around the ballpark during his recovery."
The 37-year-old has been sidelined since the start of the season with numbness and weakness in the right shoulder.
He began the campaign on the disabled list and had sat out for three months prior to beginning throwing sessions in mid-June. He said that the strength was coming back, but still had issues and sat out a live batting practice session on June 25.
It was then decided that surgery for the thoracic outlet syndrome was the best course of action.
In 34 starts last season, Carpenter was 11-9 with a 3.45 ERA. He also went 4-0 with a 3.25 ERA in six playoff starts.
Over 14 seasons in the majors, six with Toronto and eight with St. Louis, he has pitched in 347 games and posted a 144-92 mark with a 3.76 ERA and 1,685 strikeouts.