Wagner, one of Minaya's prized free-agent signings after the 2005 season, saved 101 games with a 2.40 ERA in three years for the Mets, before missing the first 4 1/2 months of this season recovering from Tommy John elbow ligament replacement surgery.
He will join Hideki Okajima as a left-handed setup man in the Red Sox's bullpen, then will test the free-agent market as a closer this winter.
"He's going to a team that appears headed for the postseason," Mets manager Jerry Manuel said of the Red Sox, who entered Tuesday's play leading the American League Wild Card race by 1 1/2 games. "That's got to be exciting for him -- a lot of exposure. They're a very good team, and he should do well. I'm happy for him."
Negotiations were not easy. Wagner's demands included a guarantee that the Red Sox would not pitch him more than once every three days -- his recommended workload coming off Tommy John surgery -- that they would not exercise his $8 million option for next season and that they would not offer him arbitration this winter. Doing so would force an interested suitor to relinquish two high Draft picks in order to sign Wagner, a likely Type A free agent, thereby reducing his value on the open market.
The Red Sox reportedly relented on the first two demands, but not the third. And they became convinced of Wagner's health after he fired a scoreless inning Tuesday, striking out two and touching 96 mph on the radar gun.
The Red Sox also reportedly agreed to pay the remaining $2.5 million on Wagner's 2009 salary, in addition to the $1 million buyout he will be owed once the team declines his option.
It was a last-minute success on a deal that hours earlier seemed dead. Citing his aforementioned concerns, Wagner had reportedly exercised his no-trade clause, forcing the Mets to retain his services for the rest of the season. Current Red Sox closer Jonathan Papelbon, meanwhile, made waves, telling Boston's WEEI.com that he did not want Wagner on the team.
But that was not enough to scare the Sox away. Wagner left the Mets in Florida early Tuesday afternoon and will report to Boston on Thursday, after a stop at his home in rural Virginia.
For Wagner, the move means a possible return to October baseball, which he has experienced just five times in a 15-year career -- and only once, in 2006 with the Mets, did he advance beyond the first round.
More than postseason glory, Wagner's time with the Mets was marked by consistent regular-season success -- and an outspoken manner off the field. Most notably, in 2008, Wagner gained notoriety when he called it a "shocker" that all of the team's prominent Spanish-speaking stars had left a game early, leaving postgame interview responsibilities in his hands.
Regardless, Wagner joins the Red Sox as one of the most successful closers in the history of the game. His 385 career saves rank third among active players, behind Trevor Hoffman and Mariano Rivera, and sixth in the history of the game. Had Wagner stayed in New York, he would have been unable to move further up that list, pitching behind current closer Francisco Rodriguez.
In Boston, he will not be a closer. But he will have one additional perk.
"He wanted to be part of a pennant race," Minaya said. "I want to thank Billy for the work he did here with us."