Fights against Floyd Mayweather and Oscar De La Hoya are now a reality after Hatton dismantled the former world lightweight champion over four rounds brooding with vicious efficiency.
Referee Joe Cortez counted stunned Castillo out on one knee after two minutes and 16 seconds of the round after Hatton had crashed home a breathtaking left hook to his ribs.
It was a win which could scarcely have been better scripted as he dominated Castillo from the opening bell to elevate his unbeaten 43-fight career to a whole new level of greatness.
Hatton said: “When you talk about Mayweather and De La Hoya and people like that I needed a performance like that to put myself in the shop window.
Hatton did justice to a glittering occasion which began with Wayne Rooney and Marco Antonio Barrera carrying his title belts into the ring by bullying the supposedly daunting Castillo from the first bell.
Hatton continued: “From the very first punch I threw I felt like I was hurting him and in the clinches I felt I was throwing him around like a rag doll. I knew if I kept the pressure on he surely wouldn’t last.
“I’ve thrown a fair few rib-benders in my life and I’d like to think I’m the best body puncher in the world. But to do it against someone like Castillo is quite impressive.”
Mexican Castillo enjoyed more success in the third round as he resorted to left hook body shots of his own, but Hatton never looked likely to be denied a famous win.
“He got me very good with that punch,” said Castillo afterwards. “I have never been caught that way. It was the perfect shot. I couldn’t breathe. I couldn’t get up.”
Hatton’s decisive punch was also applauded by Castillo’s veteran promoter Bob Arum, who said: “I’ve been in boxing 42 years and I’ve probably seen that shot hit perfectly five times.
Some may point out the 33-year-old Castillo might not have been quite the same fighter who twice pushed Mayweather to points and engaged in two brutal lightweight battles with Diego Corrales.
But he was still an impressive enough scalp to alert the biggest names in his sport, with De La Hoya quickly getting on the phone to hail Hatton in his dressing room.
Hatton added: “Oscar phoned me up and congratulated me. He mentioned that he’s done so much in his career and he would love to come and fight me in England.
In reality size may preclude De La Hoya from meeting Hatton in the ring, and his call may have had more to do with the imminent promotional availability of one of the hottest names in the sport.
Hatton is known to be keen on a triumphant homecoming at a stadium in either London or Manchester towards the end of the year but insists he will only accept the best opponents from here on in.
“I think that win and the manner in which I did it sets possible fights up with the likes of Mayweather,” added Hatton.
“There are a lot of good fights out there for me. I want to be fighting world champions and the best pound for pound fighters in the world.”