Many teams tend to get that extra aging 1B/DH/OF type to come off the bench and do some damage. Or, an elite defensive guy with poor offensive skills. Between all of their bench guys, they have none of that.
The one thing Aviles does, and does well--which a700 likes to ignore-- is that he kills lefties, something the team absolutely needed. The problem is, he hasn't done a whole let else this season. In general, the bench hasn't really been good at a lot of things, besides Lowrie in May, and Varitek in June.