The deal will pay Beltre a base salary of $9 million in 2010. It includes a $5 million player option for 2011 and a $1 million buyout, and is contingent upon Beltre passing a physical exam, which is expected to be performed before the end of the week, sources said.
If he does not exercise the option, Beltre will receive a $1 million buyout if he makes 575 plate appearances this season, an industry source told ESPNBoston.com. Beltre has reached that plateau every season since 2001 except last season, when injuries limited him to 477 plate appearances.
Beltre's player option is doubled to $10 million in 2011 if he makes 640 plate appearances, the source said. Beltre has eclipsed that number just three times in his 12-year career, the last in 2006, when he had 681. He missed by one in 2007, when he had 639, but at this stage of his career, and coming off shoulder surgery, it would seem unlikely Beltre reaches that number this season.
Beltre, a 12-year veteran, batted .265 with eight home runs and 44 RBIs for the Mariners last season, in which he was limited to 111 games due to injuries. From 2006-08, his average numbers were .270, 25 homers, 88 RBIs and 149 games played.
Beltre's best offensive season came in 2004 for the Dodgers when he batted .334, had a league-leading 48 homers and added 121 RBIs to finish second in the MVP voting. That season led to a big free-agent contract with the Mariners, but he never again came close to matching that offensive output. Beltre was paid $12 million in 2009, the last year of the five-year, $64 million deal he'd signed as a free agent with the Mariners. Beltre was offered salary arbitration by the Mariners, but declined.
His best season with the Mariners came in 2007 when he hit .276 with 26 homers and 99 RBIs.
Beltre's career average hitting in Fenway Park is .179 and isn't that much better in other AL East parks -- .185 in Tampa Bay's Tropicana Field and .219 in the old Yankee Stadium. Boston will play 99 of 162 games at these parks.
Many teams looked at Beltre, however, for his defense. He won Gold Gloves in 2007 and 2008. The Red Sox have had Mike Lowell at third base, but he has been limited by injuries.
A source told ESPNBoston.com's Gordon Edes last week that even after the Lowell trade with Texas was nullified by the Rangers, the Red Sox had quietly continued their pursuit of Beltre through agent Scott Boras.
The abortive Lowell deal complicated matters, since the Red Sox are obligated to pay Lowell $12 million in 2010. The proposed deal with Texas had called for them to pay $9 million of his salary to the Rangers in exchange for minor league catcher Max Ramirez.
A baseball source told ESPN.com's Jerry Crasnick that the Red Sox have talked to the New York Mets about a possible Lowell-for-Luis Castillo trade. But there are several obstacles to the deal, and it's uncertain how motivated either team would be to make it happen.
Lowell would have to move to first base in New York, because David Wright is already entrenched at third.
By moving Castillo, the Mets would be free to make a play for free-agent second baseman Orlando Hudson. But Castillo has played all 1,609 of his career games at second base, and Boston already has an All-Star second baseman in Dustin Pedroia. The trade probably wouldn't work for the Red Sox unless they were able to flip Castillo to a third club.
But the Red Sox now have quite a bit of money committed to third base.
The Orioles and Angels were also thought to be interested in Beltre.
The Orioles did sign infielder Garrett Atkins, but that did not seem to preclude them from moving on either Beltre or free-agent first baseman Adam LaRoche. The Angels lost their third baseman, Chone Figgins, to Seattle, Beltre's former team, and while they have indicated they plan to give in-house candidate Brandon Wood a crack at the job, they might have turned to Beltre if his asking price had dropped.
The Athletics were thought to be interested but dropped out of the bidding, an industry source told Edes. Oakland could use a third baseman given the ongoing health problems of incumbent Eric Chavez.
ESPN.com's Jerry Crasnick and ESPNBoston.com's Gordon Edes contributed to this report.