BOSTON – First, the Red Sox were determined not to go beyond three years for free agent third baseman Mike Lowell. Then, they placed an expiration date on their proposal.

Today, their strategy paid off. Lowell and his agents agreed to a three-year deal worth $37.5 million. Only some last-minute paperwork needs to be completed.

An official announcement could come as soon as tomorrow.

Under the terms of the new deal, Lowell, who earned $9 million in each of his first two years with the Red Sox, will be paid $12 million in 2008, 2009 and 2010 and will be given a $1.5 million signing bonus up front.

The agreement came after the Sox last week informed Lowell and his agents – Sam and Seth Levinson – that their offer would come off the table after today. The Sox were concerned that their ability to craft a fallback plan for Lowell’s replacement would be hindered by having the negotiations for the free agent drag deep into the off-season.

The Sox had mulled the possibility of moving Gold Glove-winning first baseman Kevin Youkilis back to his original position at third and pursuing a first baseman. They also investigated the availability of more established third basemen such as Hank Blalock and Garrett Atkins.

In returning to the Red Sox, Lowell passed on the chance to land a four-year guaranteed deal elsewhere. While reports of four-year offers from the Atlanta Braves and St. Louis Cardinals were publicly denied, he had attracted interest from the Philadelphia Phillies, Los Angeles Dodgers and Los Angeles Angels of Anaheim.

The Angels and Dodgers were both also involved in talks for Lowell’s replacement at third for the Florida Marlins: Miguel Cabrera.

Lowell had been courted by the New York Yankees before the Yankees re-started talks with Alex Rodriguez, but all along, the Yankees – who originally drafted Lowell in 1995 -- expected that he would return to Boston. For a time, the Yankees toyed with the idea of moving Lowell to accommodate Rodriguez, but Lowell was said to be less than enthralled with that prospect.

He led the Red Sox in RBI and set a career high in that category with 120 this past season, then capped his year by being named MVP of the World Series. It was Lowell’s second championship – he won his first title with the Florida Marlins in 2003 – and he made it clear that his first preference was to stay with the Red Sox.

Lowell reportedly debated the offer with his family over the weekend, then instructed the Levinsons to get a deal done this morning.

Obtained by the Red Sox as part of the deal for Josh Beckett in November 2005, he was originally viewed as something of an expensive anchor whose inclusion in the deal was necessary for the Sox to land Beckett.

He had his worst season in 2005, hitting just .236 with eight homers and 58 RBI. But he bounced back in 2006 to hit .284 with 20 homers and 80 RBI and play superb defense at third.

This past season, he hit a career-best .324 with 21 homers and 120 RBI and was arguably the team’s MVP.

His return enables the Red Sox to begin the 2008 season with virtually the same lineup they had in the World Series – with every position player returning, the starting rotation intact and the principal bullpen members under the team’s control.

That’s quite a departure from the 2004 World Series club, which underwent a dramatic overhaul in the months between the franchise’s first championship in 86 years and Opening Day the following spring. That year, the Sox lost two starting pitchers (Derek Lowe and Pedro Martinez), their double-play combination (Orlando Cabrera and Mark Bellhorn) and would go on to lose their corner infielders (Bill Mueller and Kevin Millar) and leadoff hitter (Johnny Damon) the following offseason.