The Sox have two really good 1B on the roster, plus a couple of other passable ones. He isn't starting over Abreu. Vaughn is also ahead of him there. You still have guys like Collins and Grandal who can play over there.
The Sox have a roster full of DHs.
Gavin Sheets has not shown that he can play as passable OF, unless you also consider Daniel Palka a passable OF.
A guy like Burger is going to be more of a roster option as he can at least play 3rd.
The Sox still have to figure out how to roster Eloy, Robert, and Grandal for sure. Jake Lamb might be coming back as he is on rehab.
It's a numbers game.