Dr. James Andrews, who performed the surgery, repaired the ulnar collateral ligament in Hanrahan's elbow as well as the torn flexor muscle with which he was originally diagnosed. Andrews also removed bone spurs from the elbow, Mike Dillon of Reynolds Sports Management said in a tweet.
Typically, a pitcher is out from 12 to 16 months after undergoing Tommy John surgery. Hanrahan is a free agent at the end of the season, so it is conceivable he has thrown his last pitch in a Red Sox uniform.
Red Sox reliever Andrew Bailey, who had just been named the team's closer in Hanrahan's absence before he went on the DL with a strained right biceps, is on track to be activated Monday in Chicago, manager John Farrell said Thursday.
Bailey will slide back into the closer's role on Monday, Farrell said. Bailey threw a simulated game here Thursday and is scheduled to make a rehab assignment Saturday for Pawtucket. Assuming that goes well, he'll rejoin the team after being on the disabled list since May 6, retroactive to April 29.
Bailey last pitched on April 28, when he pitched a scoreless ninth inning, allowing one hit, against the Houston Astros. Before being hurt, Bailey had run off five saves in five chances, striking out 11 in six innings and holding opponents to a .100 batting average (2-for-20).
"I watched him out here today," Farrell said. "He threw the ball very well, not only with power with his fastball but action with his secondary stuff."
Junichi Tazawa has served as closer in the absence of both Hanrahan and Bailey. Tazawa did not have any save opportunities, but entered the ninth inning of a tie game against Toronto last Saturday and gave up what proved to be a game-winning home run by Adam Lind. He has not pitched since.