The Hitman's corner man reckons Hatton is still getting better and that the world light-welterweight fight against the Mexican at the Thomas and Mack Centre on June 23 will blow away the doubters.
Hatton has endured flak from critics who claim he has been on a downslope since beating Kostya Tszyu two years ago, and who say his indulgent lifestyle when he is not in training has taken its toll.
But Graham, who has never made a secret of the fact that he would like Hatton to tone down his eating and drinking between fights, says Castillo is the perfect foil for his fighter's aggressive talents.
Tactics
And even at the age of 28 and after 43 straight wins as a professional, he says the Hyde hero is still getting better.
"He is learning all the time - he especially learned a lot from the last fight against Juan Urango," Graham said.
"He had to change tactics because he was suffering from a virus, and it's something we both learned from.
"He is also gaining in experience, obviously, and is even getting a little bit quicker and stronger. You can measure his strength on the weights because of the poundages he is lifting, and I can measure his speed when I work on the pads with him.
"He has been able to throw every shot in the book for a long time now, but it was about getting a little bit better tactically and a bit more experienced."
Hatton has been criticised for his last three performances, even though he knocked out Carlos Maussa for the WBA light-welterweight title after initially finding the Colombian's windmilling style awkward, then showed some grit to hold a lead against the much bigger Luis Collazo in his only venture at welterweight, and boxed beautifully in the early stages of his points win over Urango on his Vegas debut in January.
But Graham says he has no time for the snipers. "There are reasons why his last three fights have not been so-called `stellar performances.'
"I am expecting Castillo to bring out the best in him, but Ricky will also bring out the best in Castillo. Their styles will gel and the fans are in for a real treat.
"When he was a kid I told him he would be judged very harshly by the press because of how talented he is. But they have taken it to the extreme. I can't believe some of the negative things that have been said.
Ambassador
"He is the best ambassador British boxing has ever had, and I also believe he is the best fighter British boxing has ever had. Anyone who can't get 100 per cent behind Ricky Hatton has something wrong with them."
Hatton and his team flew to Vegas last week, giving him over two weeks to acclimatise and shake off the effects of travel, but Graham says there will be no difference in his final preparations for what promises to be Hatton's toughest fight, after Tszyu.
"The only thing different is staying in a house to avoid the air conditioning in the hotel, but won't be doing anything different because it's been a winning formula for Ricky for years as well as the other fighters I have trained," said Graham.
"We had some Mexican sparring partners waiting for us when we arrived, and sparring has gone well."
One Mexican has already felt the heat of Hatton's desire, with Enrique Colin Reyes ending up in hospital after a sparring session at Hatton's Denton gym.
But most sparring partners struggle to keep pace with Hatton's relentless pressure and body punching according to Graham.
"Reyes started off like most people who get in with Ricky but after a couple of days he was a bit worn out and had to go to the hospital with damaged ribs," he said.
Training
"When Ricky started out with me, training in Salford, we had a few fighters round about his weight but in recent times we have had to draft sparring partners in and, to be honest, with a couple of exceptions, they have not been able to take the work. The problem with Ricky is that the only people who can stay with him in sparring for more than a couple of sessions are the people who you know he may fight one day.
"It's a big ask, so we usually import them two at a time, and bring in fighters who are bigger than Ricky. He is a punishing fighter and a terrific body puncher and he soon wears out sparring partners."
Hatton always prepares meticulously, but Graham says he can sense a new sense of purpose in his man for this contest:
"He is really up for this fight. It hurts him when he gets panned by the critics after doing everything right.
"He should have been praised for that last performance against Urango, and for Collazo and Maussa, all difficult fighters and world champions, one of them at a higher weight.
"I have seen fighters praised for far worse performances."
Do you think the fight will be a tactical battle or a war? Have your say.
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