The move could help pave the way for Franklin Morales to move back to the rotation, where he had success in June and the early part of July, although the Sox were non-committal Tuesday.
Breslow, who turns 32 in eight days, is 2-0 with a 2.70 ERA this season -- his first in Arizona after being dealt from Oakland in December as part of the Trevor Cahill deal. Breslow has struck out 42, walked 13 and allowed five home runs in 43 1/3 innings.
"Very excited to return to Boston," Breslow told MLB.com. "Some things have changed since my last stint, but one thing that hasn't is the commitment to winning. I look forward to meeting new teammates, rejoining old ones and doing my part to help the organization."
Albers, 2-0 with a 2.29 ERA in 40 outings, said the trade was unexpected and that the club he leaves behind was "definitely the most talented I've ever been on."
"I have a lot of good memories from playing in Boston," said Albers, who signed with the Sox prior to last season. "A little surprised. I really didn't, wasn't really expecting it. I don't really read the trade rumors, 'cause obviously a lot of it's just you never know whether it's actually going to go through or not. ... Nothing I can do. It's a done deal now. I can't think about what it was like here. It's over with."
A New England native and a Yale graduate, Breslow's been here before, pitching for 13 games for the Sox in 2006. He went 0-2 and gave up five runs in 12 innings (3.75 ERA) with the Sox, who signed him as a free agent. He stayed in the organization until the Indians claimed him off waivers in March '08.
When Breslow arrives, he'll join the Sox with a preexisting rapport with his manager and injured reliever Andrew Bailey -- all Connecticut natives. Bailey and Breslow became close as teammates on the A's for three years, and Bailey hosted a charity event to benefit Breslow's foundation in Connecticut this winter.
"Breslow is coming to give us that left-handed depth in the bullpen," said manager Bobby Valentine, who also attend Bailey's charity event. "He's having a nice year. I haven't seen him pitch too much. I know he's been in the American League before. ... I know he was here before.
"It's not as I've known him for 100 years. He is, from what I hear, the second best athlete out of Trumbull High School. Chris Drury came out of the same high school. I've been at two charity events with [Breslow]."
Breslow's been on six teams in seven seasons -- seven if the Red Sox are now counted twice -- and is 14-17 with a 3.02 ERA lifetime. His career numbers against right-handed and left-handed batters run almost parallel: righties have a .224/.314/.338 line against him, while lefties carry a .229/.291/.352 clip.
Breslow is under team control through next season, the last year he's arbitration-eligible.
Before the Sox brought Breslow back, Morales and Andrew Miller were the only two lefties in the bullpen. Now more options are available to them. Morales impressed in his five starts this season, going 2-1 with a 3.42 ERA and a 31-to-8 strikeout-to-walk ratio.
"I think if he helps us win games, I'd like to see him in the rotation," general manager Ben Cherington said. "If he helps us win games out of the bullpen, that's where I'd like to see him. It's going to depend on what Bobby and his staff are seeing, perhaps what the matchups look like. Aaron Cook has done a pretty good job for us generally since he's been here. It gives us a little more flexibility if we look ahead and see matchups that are favorable. We're glad to have that flexibility."
Valentine said that the 29-year-old Albers "did not fall out of favor with our team."
Podsednik, a 36-year-old veteran and starting player for the World Series champion White Sox in 2005, was expendable once Boston's outfield got healthy again.
In fact, Podsednik had performed well for Boston after being summoned from Triple-A in May. He hit .387 with one homer and seven RBIs in 19 games for the Red Sox, but he injured his groin on June 17.
Once he was healthy, Podsednik returned to Pawtucket, where he was until Tuesday's trade.