Manny wins. JL Castillo is overrated a bit, he was slow. Castillo was knocked out by Javier Jauregi twice, and struggled badly vs Stevie Johnson both times. Pac is better than both.
Pac by stoppage. Castillo did not have the defense to avoid the inevitable. Castillo was vastly inferior skill wise to his mentor, JCC Senior. He had a decent chin, but nowhere near the concrete JCC packed. These two liabilities would prove too costly against a frenetic punching Manny in his prime.
Pacs all wrong for Castillo, he'd win a wide UD I think, although maybe not as Castillo was pretty smart.
Castillo was a volume puncher, Manny was as well. But Manny was much more precise. He wears down Castillo in 6-8 rounds and winds up Koing him coming in. Castillo was an outstanding boxer/ Mauler and he would force Manny to counter. Something when given the chance suited Manny very well. Outstanding shootout with the edge going to Manny, His Power and speed and accuracy would dent then finish Jose. Before this I see Jose winning the fight on points by a slight margin. Once Castillo is hurt Manny wont let him off the hook. That is the difference between the mayweather bout and this one. Power Manny > Mayweather