I suspect hatton will win this in impressive fashion. I believe Hatton will get to Castillo in the later rounds and force a stoppage, maybe the 8th round. Hatton should adopt his in and out approach he has used so well in previous fights namely Tackie and Olivera and wear Castillo down. Not to take anything away from Castillo as he's my kind of fighter but he has a lot against him here, Hatton's footwork , angles , and speed are superior to his. Castillo fits the 140's nicely and looks in no way blown up but i doubt his power at 140 and add to that Hattons chin and he has problems. The only way he can get to Ricky badly is via the body imo and he will look for that all night.
But in general i am anticipating a great fight.
Hatton TKO 8/9