"There was only me left and he couldn't even do that in the end. It was the toughest decision of my life to leave Billy but it was the best one.
"They were putting needles in his hands to numb the pain so he could take a training session. When I hit him he would say, 'you're hitting too hard', but in my mind I was thinking, 'well you don't know because you can't feel your hands'.
"He was deluding himself and didn't want to admit to himself that the time had come to finish. Everyone was telling me to leave him earlier.
"I couldn't do it because of how I had such a close relationship with him but when Matthew left I knew I had to be a man and leave as well."
The Manchester fighter will be returning to the scene of his only defeat, which came against Mayweather's son, Floyd Mayweather Jr, at the MGM Grand in Las Vegas last December.
Mayweather Sr has trained a host of world-class fighters, including six-weight world champion Oscar de la Hoya, who he recently left in order to concentrate his efforts on Hatton.
And the American, who was a very respectable boxer who once fought the great Sugar Ray Leonard, believes he can make Hatton a "slicker, smarter" fighter.
Mayweather told BBC Radio 5 Live: "I know I can make a change in him. I'm trying to get him to throw combinations, not just one-two, but one-two-three-four-five.
"It's a very good fight for him, Ricky's got a very good chance of stopping Malignaggi and he'll be hit a lot less. What Ricky did, he did on his own. He was throwing one punch at a time, he could barely throw a combination.
"I'm going to have him throwing triple hooks, double hooks, single hooks, hooking off his jab, a mixture of a lot of different combinations. I want him to get slicker and smarter. You'll all see a big difference."
Hatton hopes to beat 27-year-old New Yorker Malignaggi next month and then fight the winner of the match between De la Hoya and Filipino legend Manny Pacquiao, which takes place on 6 December.
And he conceded he would probably retire if he loses to Malignaggi, the IBF light-welterweight champion who has been defeated just once in 26 professional encounters.
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