Although the Red Sox have not placed a timetable on Bailey's return, manager Bobby Valentine said he was told by the training staff that Bailey should not be expected to return before the All-Star break.
Bailey was examined Monday in Boston and Tuesday in Cleveland. The surgery is scheduled to be performed by Dr. Thomas Graham in Cleveland, the Red Sox said in a statement.
The UCL is located at the base of the thumb.
"We won't use him until he is fully recuperated. Guys we have set up in the bullpen will hold down the fort," Valentine said.
Valentine isn't sure how Bailey was injured. The manager initially said it began bothering the closer during a game against Pittsburgh on March 21, but Valentine wasn't aware of it until Friday.
"When I talked to him before he left, he was unknowing," Valentine said. "He felt a little something. There really wasn't a defining moment, in the last conversation I had with him."
Valentine did not name a new closer, but he said that Mark Melancon is among those who will get the chance to
close games out.
"It is unfortunate Bailey is out," Melancon said. "I just heard the news.
We have a good bullpen. We will be all right. We are going to figure it out. I am ready (to pitch
the ninth if need be)."
Melancon, who pitched in nine games this spring, posting an 0-1 record with a 5.59 ERA, and had 20 saves last season with Houston, said he had not been told by Valentine that he would be the closer.
Another candidate for the job would seem to be Alfredo Aceves. Aceves, who also said he was unaware of Valetine's plans for replacing Bailey, appeared in six Grapefruit League games, going 1-1 with three saves and a 5.21 ERA. He has four career saves over four major league seasons.
Daniel Bard, who was moved to the rotation, has been mentioned as a candidate to go back to the bullpen, but Red Sox general manager Ben Cherington shot that down earlier Tuesday.
"(Bard) is going to pitch Game 5 in Toronto and we're committed to him as a starter right now," Cherington said, according to NESN.
Valentine said he supports the decision to leave Bard in the starting rotation.
"I think he is finally feeling pretty
good about being there," Valentine said. "There is no use to change strokes in midstream."
Valentine said the closer's role "will evolve early in the season. I am confident we have pitchers that can get the final out of the game. It is just the rest of the (bullpen) that is a work in progress.
"I would be telling you something that was less than truthful if it was something we had prepared for. I like to think that we have a plan in place, that we have a person that we can single out for that (closer's) role, along with others who can do it when he is not available. That is how it was when Andrew was there."
Bailey was acquired in a December trade with Oakland to replace Jonathan Papelbon, who left in the offseason to sign a $50 million, four-year contract with Philadelphia. Bailey was also sidelined at the start of spring training when he strained a lat during the vertical leap portion of his entrance physical, but returned to pitch six innings in six Grapefruit League games, with an 0-1 record and a 4.50 ERA.
Bailey also missed time with injuries each of the last two seasons. He began last year on the disabled list with the Athletics because of a strained right forearm, and in 2010 was sidelined with a right intercostal strain and later had right elbow surgery.
Red Sox starter Clay Buchholz had Bailey on his mind Tuesday while talking
to reporters after Boston's game against Washington.
"That is a tough break. Everybody feels for him," said the right-hander. "He will play a big role on this team when he gets back. It is big shoes to fill."
Red Sox outfielder Ryan Sweeney said: "Obviously he was a huge key of what we are about. Obviously we are going to miss him. We have a lot of guys who can come in and do a good job."
Red Sox starter Josh Beckett also was in Cleveland getting his right thumb examined by Graham, a noted hand and wrist specialist who previously performed surgeries on Kevin Youkilis and Jarrod Saltalamacchia. Valentine said the news coming out of Cleveland on Beckett's thumb was all positive.
Beckett had his thumb examined on Monday by Dr. Mark Bagg in San Antonio and wanted another opinion to ease his mind.
"The good news is the situations do not seem to be the same. The bad news is they don't seem to be the same," Valentine said with a wry smile, talking about the injuries to both pitchers. "One seems to be a problem and one seems not to be. Beckett is the latter."
Valentine said he fully expects Beckett to make his scheduled start on Saturday.
Asked to describe the difference in the injuries, Cherington said: "(Bailey's injury) is different because we think it's more an of acute injury. We think it was suffered when he was in a collision in Bradenton. He was covering first and collided with Alex Presley and fell.
"At the time, he didn't think anything of it, but he started to experience some soreness shortly after that and then went back and looked back at the video and he definitely landed on the thumb. He never had any thumb soreness before that. You never know for sure, but that's a possibility that's what did it. Any time you have more of an acute injury you have to get to the bottom of how bad it is and whether it can be managed conservatively or not.''
Valentine said Monday that Beckett threw 100 pitches on Sunday in a controlled bullpen session and "felt great."
It remains unclear how Beckett injured his thumb. Valentine said Beckett has "a little history with it," saying it's not a blister but "just a little situation."
Valentine also said he discussed the Opening Day roster with Cherington on the flight from Florida to Washington, D.C., Monday night.
"We had extensive meetings this morning with coaches and we're all pretty well set," Valentine said of the roster. He added the roster would not be announced until the 11th hour.
ESPNBoston.com's Gordon Edes, Rick Weber and contributor David Driver contributed to this report. Information from The Associated Press was also used in this report.