It was the worst-case scenario for righthander Joel Hanrahan, who went in for surgery by Dr. James Andrews on Thursday.
In addition to flexor tendon surgery, Hanrahan required Tommy John reconstruction surgery to repair a torn ulnar collateral ligament in his elbow. He also had bone spurs removed, according to one his agents, Mike Dillon.
Hanrahan is expected to miss 12-15 months recovering from the surgery. The 31-year-old will be a free agent after the season.
Hanrahan, who was obtained from Pittsburgh in December, appeared in only nine games for the Red Sox.