First of all this is my own personal conjecture....not a rumor or something I read. Now that the clarifier is out there my idea:
The Sox signing of Castillo and trade for Cespedes puts the quintet of Betts/Boaegarts/Holt/Cecchini/Bradley Jr. in play especially for pitching. A deal of either Latos or Cueto for 1 or 2 of these guys and possibly a third lower level guy could give the Reds an OFer, or in Holt's case a versatile IF-OF guy. The Sox system is loaded yet starting pitching remains their big need - one team that could afford a prospect rich package and still have a strong farm, that also has a need the Reds can match....