If I'm the Sox, I would be thinking really hard about a guy like Justin Upton. I was thinking about him tonight as I watched Curtis Granderson. I remember when the Yankees got Granderson I thought it was a decent signing, but not a difference maker. He had some good numbers and some poor numbers, was relatively young, but was inconsistent in Detroit. Obviously, since then Granderson has been tremendous and fits nicely into the middle/bottom of that Yankees lineup making them a powerhouse.
It's easy to look at Upton's season and relative inconsistency and write him off as not worth investing in. However, we have to remember that he's going into his age 25 season. Granderson had 202 PAs going into his age 25 season. Upton has 3030 PAs already. I think he's the type of player the Sox would think about investing in even if it costs guys they would otherwise like to have.
Say they make Bogaerts and one or two of Webster, Barnes or De La Rosa (whoever they like the most) unavailable; leaving two of those pitchers, Jackie Bradley Jr, and almost everyone else available.
They would still have enough money to make a run at Ellsbury (or any significant FA, for that matter) and would give them a young offensive core of guys like Middlebrooks, Bogaerts, and Upton to build around moving forward.
I'm not convinced that Upton is the guy. I do think that he's relatively affordable, very young and might be cheaper than usual after a down season and rumors flying that he's done in Arizona. Yes, pitching is the #1 priority, but neglecting other needs because of a myopic focus on the #1 priority would be just as bad as not addressing #1 well.