In return, the Marlins acquired Hunter Jones and Jose Alvarez.
"We're getting two left-handed pitchers. One of them, Hunter Jones, we think will compete for a bullpen spot in Spring Training," Marlins president of baseball operations Larry Beinfest said. "Big guy, he has three pitches. It's an opportunity to add a pitcher we think can compete for a big league job.
"The young guy [Alvarez] had really good numbers in Class A ball. He's started and relieved. He's a strike thrower and he's a winner, and we like that. As far as Jeremy goes, he had a lot of opportunities here. We wish him well."
Hermida spoke late Thursday afternoon to Red Sox general manager Theo Epstein, and the trade was announced shortly thereafter.
"You kind of figured it was coming from the business side of it," Hermida said. "You look back and I had a great time with the Marlins. I'm definitely going to miss it here. I made some great friends and they treated me very well here. It was a blast to be here.
"On the other hand, I'm very excited to go to a city like Boston and a team like that. There isn't a better team, in comparison. Just the history and the fan base that they have. I'm very excited to go up there and be a part of that as well."
The 11th overall Draft pick in 2002, Hermida comes off a rough season. He batted .259 with 13 home runs and 47 RBIs. The Marietta, Ga., native missed the final few weeks of the season with a right oblique strain.
"Our expectations were high for Jeremy," Beinfest said. "He had his moments where he was highly productive, like the second half of '07. But, given his talent level, I think the expectation was for more. Hopefully he'll realize [his potential] elsewhere."
After making $2.25 million in 2009, Hermida was lined up for a pay raise in his second season of arbitration.
The Marlins' payroll in 2010 is expected to be at or slightly less than the $36 million it was in 2009.
Florida expects to bring back Cody Ross, who also is eligible for arbitration, to play right field. The team's outfield projects to be Chris Coghlan in left field, Cameron Maybin in center and Ross in right. Coghlan, however, may wind up at second base. There is a strong likelihood that Dan Uggla will be traded.
If Coghlan moves back to the infield, the Marlins have several outfield prospects, including Scott Cousins and Mike Stanton.
"If Maybin slides into center field, Cody can play right," Beinfest said. "Stanton and Cousins are on their way. We thought we were dealing from an area of depth. And also, within our payroll, our allocations need to be in the best place to be most competitive. Obviously, [Hermida] is a second-time arbitration player."
Jones, 25, spent 2009 with Triple-A Pawtucket, where he was 4-3 with a 4.25 ERA in 36 relief appearances.
A native of Palm Beach Gardens, Fla., the home of Marlins right-hander Chris Volstad, Jones attended Florida State.
Jones made 11 relief appearances with the Red Sox in 2009, giving up 13 runs in 12 2/3 innings.
Alvarez, 20, combined for a 9-4 record and 2.26 ERA in 26 games, including 12 starts.
At Class A Carolina, he was 1-1 with a 4.74 ERA in 12 games. And at Class A Lowell, the Venezuelan native was 8-3 with a 1.52 ERA in 14 games, including 12 starts.
Hermida will get a chance to establish himself in Boston, where he could play either corner outfield spot.
In the final weeks of the 2005 season, Hermida was called up by the Marlins, and he was briefly a teammate in Florida with Josh Beckett and Mike Lowell.
Beckett and Lowell, of course, were traded to the Marlins after the 2005 season in the deal for Hanley Ramirez and Anibal Sanchez.
Overall, Hermida is disappointed that his tenure with the Marlins wasn't more productive.
"The past couple of years, it didn't quite turn out the way I'd have liked to map it out on paper," Hermida said. "I still had a great time here. But I'm looking forward to the situation I'm in now. I'm getting a fresh start. Hopefully, I can take off.
"[Theo] told me, they were excited to get me. I'd been on their radar for a long, long time, and they wanted to get me part of the Boston Red Sox. They said we'll be in touch the next couple of days and give me more detail. He expressed his excitement in getting me on the team."
Hermida made a historic MLB debut. On Aug. 31, 2005, he belted a pinch-hit grand slam in his first appearance. He became the first player to hit a pinch-hit grand slam in his first at-bat.
Hermida opened 2009 in left field, but he moved to right field in May after Coghlan was promoted from Triple-A New Orleans.