Julian Tavarez, who did a solid job in the rotation when given the chance in September, will take Papelbon's starting slot.
This, after a winter and spring in which the Red Sox and Papelbon both said numerous times that the hard-throwing right-hander would go into the season as a starting pitcher for medical reasons.
Just when it seemed that only the massive constituency that makes up Red Sox Nation was losing sleep over the team's lack of a closer, Papelbon confessed that he was also tossing and turning at night. As it turns out, he couldn't get the thirst for closing out of his blood. In fact, Papelbon said Thursday that he now wants to be a closer for "the rest of my career."
After agonizing over it for weeks, Papelbon finally took his thoughts to manager Terry Francona before Monday night's game against the Twins. After two days of organizational meetings, Francona and general manager Theo Epstein officially signed off on the move.
"For me, it's been a thing that I've been thinking about all spring," Papelbon said. "I hadn't been sleeping well since the whole Spring Training started. I felt that there was always that feeling deep down in my heart that I wanted to close.
"For me, it just kept getting at me and getting at me until finally I went to our captain [Jason Varitek] one day and I said, 'Tek, I'm not sleeping good at night. I've got to do something about it.' Basically I told him, 'Man, I think I want to close -- that's what I want to do.'
"Tito happened to be walking by. We came in and I told Tito, 'If you want to give me the ball in the ninth inning, I want it,' and that's basically it."
The biggest hurdle to moving Papelbon back to the bullpen was cleared at the outset of Spring Training when the pitcher passed his physical with flying colors.
"He's off the charts with his strength," Francona said.
If not for the shoulder subluxation that Papelbon suffered on Sept. 1, 2006, he never would have been moved out of the closer's role in the first place.
At the end of last season, the Red Sox, citing advice from the medical staff, announced that Papelbon would be best suited, at least in the short term, to go back to starting.
But Papelbon progressed faster with his conditioning program than the club expected, enabling the eventual green-lighting of a move that Red Sox fans have been wanting for weeks.
"The most significant news about Pap is he reported to Spring Training with a completely rehabilitated and reconditioned shoulder, and it measured as one of the two or three strongest in camp," Epstein said.
Then why did the Red Sox wait so long before making the Papelbon/Tavarez switch?
Mainly because they wanted to make sure his shoulder continued to respond favorably to each outing.
"We made the decision with extensive, intense and passionate talk that we're going to move Pap to the bullpen," Francona said. "This has not been something the last four or five days -- this has been a month. I wanted to go through the proper procedures and, ultimately, I needed to talk to this young man. He actually beat me to the punch."
Last Spring Training, Papelbon impressed the brass so much that he supplanted Keith Foulke as the closer in the third game of the 2006 season. Papelbon responded by pitching his way on to the American League All-Star team and finishing second to Justin Verlander in the American League Rookie of the Year voting.
Papelbon posted an 0.92 ERA, which was the eighth-lowest in Major League history among pitchers with at least 50 innings. He was perfect in his first 20 save opportunities and went 35-for-41 overall.
"You can have these arguments, as baseball people do, value to a club, starter or reliever," Francona said. "Normally, I go along with the argument of starter -- not in this situation. He's unique. He's at the top of the list in all relievers in baseball. He impacts a ballclub like very few pitchers in the league."
Papelbon is as ambitious as he is confident. His goal is to emerge into Boston's version of Mariano Rivera.
"This is something that I would like to do for the rest of my career and kind of just forget about starting, and go out there and chase records and go out there and ... hopefully what Rivera has done for the Yankees, I can do with the Sox," Papelbon said.
Francona noted that he needs to be careful not to overuse Papelbon, as he was admittedly guilty of at times last season.
"Restrictions isn't probably the correct word," Francona said. "I think common sense and good judgment. We went to him deep last year. We went to him early, we went to him often, [and] we went to him with no outs in the eighth. He went sometimes 40, 45, 50 pitches. Again, if our bullpen is to the point where we have to do that, we're not in a position to win."
Papelbon also put the onus on himself to maintain the strength of his shoulder.
"If I go through this season now knowing what I know about my shoulder and do the things that I'm supposed to be doing as far as my program, my strength, my conditioning, there's no reason why I can't pitch into October," Papelbon said.
Though Papelbon was a closer at Mississippi State, the Red Sox drafted him as a starter in 2003. Until last spring, that was how the club viewed Papelbon for the long-term. They took that same view again after last year's injury scare.
"From a long-term asset management standpoint, it would have been great to keep Pap as a starter and make an apples-to-apples comparison," said Epstein. "But sometimes what looks good on paper doesn't play out in reality. I think it's all been well thought out, and we're extremely excited to have Pap back in bullpen."
As for Tavarez, he seemed to become reinvigorated when Francona moved him to the rotation in September. The righty went 3-0 with a 4.01 ERA in six starts. He fired a complete game, 7-1 victory at Toronto on Sept. 22.
Tavarez, along with Mike Timlin, Joel Pineiro and Brendan Donnelly, had been viewed as the four closing candidates for Opening Day. But all that changed with Thursday's announcement.
"I thought [Tavarez] did a great job in September," Francona said. "His ability to give us five, six, seven innings -- I don't think will be a problem. He has a knack of having some quick innings and wiggling out of nasty innings and you look out there in the sixth, he's out there with a pretty good chance to win."
Both pitchers geared up for their new -- and old -- roles Thursday. Tavarez pitched 3 2/3 innings in a Minor League game back in Fort Myers, scattering four hits and allowing no runs while striking out four. He threw 63 pitches.
Papelbon worked in relief of Tim Wakefield in Boston's game against the Phillies, striking out three and allowing a run over three innings.
"It's impressive what he does," Francona said. "Mariano Rivera has been doing it for a long time. But this kid's special -- he just hasn't done it over years yet. This kid's as good as there is. You hear him come through that gate at Fenway; it's a good feeling."
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.