Bailey was examined Monday by Dr. Mark Belsky and Dr. Matthew Leibman in Boston and Tuesday by Dr. Thomas Graham in Cleveland.
"It was determined that Andrew should undergo surgery to reconstruct the ulnar collateral ligament in his right thumb," the Red Sox said in a statement. "The surgery is scheduled to be performed by Dr. Graham tomorrow in Cleveland."
Bailey and starter Josh Beckett were in Cleveland to have their respective right thumbs checked out. Beckett came out fine and is still scheduled to start in the season's second game, on Saturday in Detroit.
"Only good news [for Beckett]," manager Bobby Valentine said.
Valentine said he thinks the Red Sox won't be able to use Bailey again until the middle of the season.
"I don't think it will be before the All-Star break, [that's] what the trainer told me," Valentine said. "We won't use him until he's fully rehabilitated."
The Red Sox are unsure when Bailey got hurt, but it's possible the injury occurred March 21, when he collided with the Pirates' Alex Presley at first base in Bradenton, Fla. Bailey threw 26 pitches in a Minor League contest Wednesday, but he hasn't faced Major League hitters since March 25.
In six Grapefruit League appearances, Bailey went 0-1 with a 4.50 ERA, notching seven strikeouts and allowing just one walk. Bailey hasn't had more than 50 regular-season appearances in each of the last two seasons.
With Bailey sidelined, Mark Melancon or Alfredo Aceves could serve as Boston's closer, but Valentine didn't want to disclose exactly who will do what in the Boston bullpen. Everything's settled, he said, and the Sox will talk more about it once they get to Detroit, where they open their season Thursday afternoon.
"The guys that you've seen in the bullpen are going to hold down the fort, do a job and help us win a lot of games," Valentine said.
The Red Sox have until Wednesday afternoon to figure out who makes the final roster. Valentine said they'll be discussing it right up until the final minute.
"Rosters don't have to be put in until 5 o'clock tomorrow," Valentine said. "We'll take all that time just to make sure."
Bailey started last season on the disabled list with the A's because of a forearm injury, and this year, he didn't make his Grapefruit League debut with the Sox until March 12 because of a lat injury.
Jeff Seidel is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.