I would prefer to get a SS as the primary piece for Robert, although I like Crawford as a prospect. Caba seems like he's got a good chance to be an MLB level SS defensively, but his offensive profile doesn't seem like more than a late order hitter who can get on and steal a base, but little else.
My hope is that the Reds are interested. I'd prefer Arroyo to Caba or Crawford, and I actually really like Chase Petty as a second piece.