Sands was never more than a piece the Sox picked up hoping he had some trade value, IMO. He was LAD's version of Mauro Gomez. Neither was ever seriously considered by either team as starting 1B potential despite moster seasons at AAA. Something about them we cannot see simply by looking at stats. If he and Pimentel can garner a top notch closer, then that is a good return value for a guy who probably never becomes a full-time player at the MLB level. If Iglesias and Melancon can bring back Sanchez, in an expansion of the deal, then the Sox have themselves covered at 1B with a much better talent without losing any meaningful parts from their 2013 team.
They may be waiting for Napoli to make a final decision on their take-it-or-leave-it offer (which I presume contains some protective language and may even reduce the contract to two years) to figure out whether to add the last piece to this deal.