Given the large number of holes elsewhere, the Sox don't really have any other option than to give Gillaspie the chance to keep up that pace. There simply aren't enough resources to fill all the other holes AND upgrade at 3B via free agency and trades. Even if he regresses to a 720 OPS, which is the worst case scenario, that is MLB average for 3B. If the Sox redirect resources to upgrade at 3B, they will be well below average at LF, DH, and C (not to mention bullpen).
So it really doesn't make sense. None at all.