Kotchman, who no longer fit into Boston's corner infield plans because of the signing of third baseman Adrian Beltre, is expected to be the starting first baseman in Seattle.
As for Hall, he figures to be a jack-of-all-trades backup for Red Sox manager Terry Francona. And if he can rediscover his form at the plate, Hall could also serve as a highly useful pinch-hitter.
Last year, which Hall split between the Brewers and Mariners, he started 59 games at third base, 22 games in left field, 12 games in right, two at second base and one game in center field.
He used to be a starting shortstop, but hasn't played that position since 2006.
The 30-year-old Hall struggled mightily at the plate in 2009, hitting .201 with eight homers and 36 RBIs in 334 at-bats. He clocked a career-high 35 homers in 2006, followed by 14 in '07 and 15 in '08.
The Brewers designated him for assignment on Aug. 12, 2009. After his breakout season in 2006, Hall signed a four-year, $24 million deal that included a $9.25 million option for '11. The Brewers are paying most of Hall's '10 salary, and the Mariners sent the remaining balance to the Red Sox as part of the trade.
The left-handed-hitting Kotchman could have been Boston's starting first baseman for 2010 if the Beltre signing hadn't worked out. In that case, Kevin Youkilis would have moved across the diamond to third.
But once Boston acquired Beltre, they no longer had space for Kotchman, who would have earned upwards of $3 million while playing a bench role. The Red Sox initially acquired Kotchman on July 31, 2009, in a trade with the Braves for Adam LaRoche. Kotchman is a gifted defender, but has yet to reach expectations as a hitter, particularly from a power department.
Ian Browne is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.