Stanton, 28, is the reigning National League MVP. He hit .281/.376/.631 with 59 home runs and 132 RBI in 2017, making him the first player with at least 59 homers since 2001.
Despite being the face of the Marlins franchise and the most feared slugger in baseball, Miami is looking to move Stanton for financial reasons. He's owed $295 million over the remainder of a 13-year, $325 million contract he signed in 2014. The deal runs through 2028 and pays him at least $25 million each season.
The Marlins' new ownership group, spearheaded by former New York Yankees shortstop Derek Jeter, is looking to cut payroll as it rebuilds the franchise. Jeter told reporters last month the Marlins are "an organization that's been losing money for quite some time, so we have to turn that around."
Stanton has been aware for months he has likely played his last game for Miami.
"It's an interesting feeling and situation for me," Stanton told reporters in November. "This is the only place I've known. But I also understand the business part of it, the direction that new ownership wants to go. ...
"The thoughts were up and down. They were pretty bipolar of everything that's going on, how [the MVP] was going to turn out and what's going to happen to my team and my teammates ... and me."
The Red Sox are a playoff team with a solid outfield, so Stanton would have been a luxury acquisition more than a necessity. They'll likely look to make moves to shore up their infield and pitching staff this offseason.