Manny Ramirez may have taken his last swings for the Red Sox, who are working on a trade that would send him to Florida, with Boston getting Pittsburgh left fielder Jason Bay and reliever John Grabow.

The Providence Journal / Gretchen Ertl

BOSTON — As if dealing away Manny Ramirez wasn’t complicated enough, the Red Sox last night were working feverishly to move the controversial outfielder in a three-team deal involving the Florida Marlins and Pittsburgh Pirates that, if completed, would give the Sox a power bat to replace Ramirez in left field and some bullpen help.

The basic structure is this: the Red Sox would send Ramirez (and cash to pay his remaining salary) and a prospect to the Marlins. The Red Sox would get two or three prospects back from the Marlins, and send them and a prospect of their own to Pittsburgh and the Sox would get outfielder Jason Bay and reliever John Grabow. The Pirates would also get Jeremy Hermida from the Marlins.

But late last night there was nothing official in place and the deal was fluid, with plenty of details still to complete. It stood an equal chance of collapsing under its own weight as today’s 4 p.m. non-waiver trading deadline approached.

The Marlins emerged fairly late in the process as a player for Ramirez. Earlier in the week, the Red Sox had sounded out the Mets, Phillies, Dodgers and Diamondbacks to gauge their level of interest in Ramirez and found little.

The prospect of the Sox paying off the remaining $7 million on the final year of Ramirez’s deal, however, enticed the low-budget Marlins to become serious bidders. The Marlins’ total payroll of approximately $22 million is barely more than the $20 million Ramirez makes this season.

In an effort to eliminate as many obstacles to a deal as possible, however, the Sox let it be known that they would be responsible for Ramirez’s entire remaining salary. The opportunity to get Ramirez for free — at least in terms of salary — intrigued the Marlins.

Locked in a three-team N.L. East race with the Mets and Phillies, the Marlins could use an offensive boost. Ramirez would be strictly a short-term rental for the Marlins, who would not exercise the first of Ramirez’s options. By offering Ramirez salary arbitration — which Ramirez would surely decline — they would be entitled to two compensation draft picks next June.

The player cost for Ramirez is relatively low for the Marlins. The two picks would immediately replace the prospects, meaning that the club gives up Hermida for two months of Ramirez..

Meanwhile, the biggest sticking point last night lay with the Pirates, who were demanding a huge return for Bay, the team’s most popular player. Bay is signed through the end of 2009 when he can become a free agent.

His salary is $5.75 million this season and $7.5 million in 2009.

The Pirates shipped outfielder Xavier Nady and reliever Damaso Marte to the New York Yankees last week for four prospects and the relatively modest return may have helped drive up the price for this deal.

Bay, who will turn 30 in September, is obviously the centerpiece of the deal from the Red Sox standpoint. A patient hitter with a career .376 on-base percentage, he has a .282 lifetime average. The National League Rookie of the Year in 2004, he’s been a two-time All-Star selection. His best season was 2005, when he hit .306 with 32 homers and 101 RBI. A year later, he established career-highs in homers (35) and RBI (109).

Grabow, meanwhile, would give the Sox a lefty specialist for their bullpen. This season, he’s limiting lefty hitters to a .240 batting average, though over the course of his career, he’s been more effective against righties (.266 batting average) than lefties (.272).

This season, Grabow is 5-3 with a 3.19 ERA in 48 games. Over the last four seasons, he’s been a workhorse for the Pirates, appearing in no fewer than 63 games each year.

Until the Ramirez deal commanded all their attention, the Red Sox were also continuing their search for other left-handed relief reinforcements.

Their interest in Atlanta’s Will Ohman is minimal, since they have questions about Ohman’s ability to pitch in a market like Boston.

The Sox remain in pursuit of Ohman’s former teammate with the Cubs, Scott Eyre. The Cubs have two other lefties — Neal Cotts and Sean Marshall — and have some depth from which to deal.

Meanwhile, the Kansas City Royals have proposed a deal that would send Ron Mahay to the Sox in exchange for Brandon Moss. Mahay, who was drafted by the Red Sox as an outfielder, then converted to a pitcher, and has emerged as one of the game’s better lefty specialists.

Mahay is in the first year of a two-year, $8-million deal. Mahay’s money next year would merely replace the $3 million the Sox are paying Mike Timlin this season. Timlin, 42, is a free agent and is not expected back in 2009.

smcadam@projo.com