Allen Craig doesn't have a very specific or guaranteed role with the Red Sox right now. He's one of their backup outfielders and also their backup first baseman, but the roster space for that gets a little cloudy when you realize Daniel Nava is out of options and can also do those things while Mookie Betts should probably be in the majors. The rest of the league realizes this, and according to ESPN's Jerry Crasnick, the Red Sox are receiving "lots of calls" for Craig from the ones hoping to make a trade. At this time, though, nothing is "brewing" on that front.
Crasnick probably wasn't making a joke about the Brewers' interest there, but they have been tied to Craig already this winter. The Marlins are presumably out on him given their outfield is full and they signed Mike Morse to play first base for them, meaning a Craig platoon with Garrett Jones is unnecessary. Other teams could end up needing Craig: for instance, the Mariners keep whiffing on their targets for outfield help to the point where Brad Miller, Major League Outfielder is in serious consideration. With very few hitters with upside left on the free agent market at this stage -- Alex Rios was considered one of the last ones, if not the last one -- offers for Craig should start coming in shortly even with his obvious downsides.
The 2014 season was a problem for him thanks to a late-season foot injury in 2013. It messed with Craig's swing and production, but he's now in the middle of a regular offseason with regular healing and regular preparation. He could be a valuable hitter once more, much like the one who slugged. 500 for the Cardinals with a 136 OPS+ for a three-year stretch prior to last year: the Red Sox aren't going to just give that away, not when he costs all of $6.2 million in average annual value, and teams desperate for an impact bat aren't going to shy away from the risk at that cost, either.