Rosario stops him. I'm fairly certain of it. Too much speed and firepower, and Castillo's toughness was overrated.
Chapo gets flack for being a front runner and I do see why... But, I think he would get so many chances at landing those clean meaty power shots that it wouldn't come into play here. It's competitive early, but I think Castillo could only take so much from Chapo. Rosario KO 8