"He turned off the bell and said: 'I'm going to spar you until you quit'"
Thursday 9 July 2020 16:00, UK
There are no clocks in Las Vegas. Gamblers and revellers are encouraged to forget the time and enjoy themselves all night but, recently, the city has been forced into slumber.
Then, suddenly in the middle of the night, the phone rings and Floyd Mayweather demands a sparring session.
"When we're sleeping, he's working," sighs the recipient of the call. Mayweather's gruelling sparring sessions have become mythology but he has been retired for three years and is 43 years old so why is he quietly continuing to box?
"Out of nowhere, he called me at 1am and told me: 'Come to the gym, I want to spar'," Denis Douglin tells Sky Sports about the voice that woke him up last month.
"I was knocked out asleep! But once he hit me up I told him: 'I'll be there right away'."
It must have been tempting to find an excuse to not stagger wearily out of bed?
"I was honoured to get that call," Douglin says. "Whether it was at 1am or 4am, I would always go.
"You have to. He is arguably the best ever and definitely the best of my generation."
Mayweather's dedication to the craft that saw him retire with a 50-0 record and as the winner of the two richest fights of all time is a source of wonder even to other hardened boxers. His nocturnal training continued even when the lights of the Vegas strip were forced to dim.
"It's not common. I heard Floyd is a super-sleeper which means he only requires five hours of sleep to function fully," Douglin said. "I don't know if that's true or not. But if it's true? He has more hours of the day than everybody else.
"When I got to the gym there was only one person there - the person who opened the gym door. When Floyd arrived? He came with 20 people. His security guards, his friends, they all came to watch."
The Mayweather Boxing Club in the middle of the night, when you arrive alone and are surrounded by the boss' entourage, is no place for shrinking violets.
"People always quit, they give up after 10 or 20 minutes," Douglin said but he was determined to survive.
The heckling from Mayweather's men, who surround the ring, begins as the top dog readies himself. It is coming from all angles and directed at one lonely soul.
"The first time I sparred him, it was intimidating. He was the man and I'd never seen anything like that," Douglin said. "Since then, I'm used to it. I actually like the audience. I make new fans when I spar in front of an audience.
"Every time Floyd lands a punch the crowd shouts: 'Ohhhhh! Ohhhhh!'
"I live for that energy. Gyms should be loud - nobody wants to fight in silence.
"We did three rounds of good work. But before the fourth round, he turned off the bell and said: 'I'm going to spar you until you quit'.
"I told him: 'Floyd, I will never quit'.
"If we're sparring until I quit then we'll be here all night.
"Floyd said: 'Okay, let's see'."
Welcome to the Dog House - Mayweather's gym has received criticism over the years for its brutal attitude to sparring. Sometimes there are no rounds, depriving a battle-weary boxer of his opportunity for brief respite. You continue until you suffer the worst indignity - quitting. All the while, the vicious jeering continues from all sides of the ring.
"We sparred for 20 minutes straight," Douglin explains.
"Devin Haney was there and he was shouting that he wanted to spar, because he had brought his own sparring partner.
"I told Floyd: 'If you let Devin spar, then you are quitting'.
"Floyd said: 'Keep going'.
"We sparred another 15 minutes straight. Thirty-five minutes in total, after doing three rounds.
"Floyd is not old, but he's old for boxing. It was great to see him go for so long, punching so hard, making adjustments. I learned a lot from things he did, from movements he made.
"I was able to land some punches and so did he. He was in excellent shape. I was very impressed by his shape.
"I was determined to not quit. It was the same for him. Nothing could have happened to make me quit.
"I wasn't hurt. I was 175lbs and Floyd was no more than 150lbs so I have a lot of weight on him. He landed good shots and his punches were hard but nothing that hurt."
Douglin is an active super-middleweight, two weight divisions above where Mayweather ended his career, and is a former opponent of George Groves.
And yet Mayweather's regime does not let up even with his bulging bank account and deep into his third retirement.
Douglin's tale echoes what Ashley Theophane, the former British champion who signed to Mayweather Promotions, previously told Sky Sports about surviving in the heartland of boxing's modern king.
"If you walk in there off the street and you're a fan or a boxer, everyone shows you love. But when you go into the ring to spar, that's when you start to hear the banging on the canvas and you just go to war," Theophane said.
"There have been many guys that have been intimidated. Guys who have been dropped or stopped in the gym. I have seen many new guys that come in there who want to impress and it just ends bad for them.
"I always remember there was one guy and he kept saying: 'Floyd won't spar me, Floyd won't spar me'. He sparred with Floyd and he got beaten up, so he should have just kept his mouth quiet, get your easy cheque. But he sparred Floyd and was terrible.
"It's nice to see the boxing skills, but there are times when it's nice to see a toe-to-toe war. He does it all in the gym.
"I remember the first time I sparred with Floyd, I got in the ring and they started to bang on the canvas and were saying 'there's a victim here, another victim'.
"You turn around and see Floyd shaking his legs and arms out, he's staring at you, and it's go."
Is a Mayweather planning a 51st fight?
"Maybe he is thinking of making a comeback or maybe he just loves boxing so much that he continues," Douglin said.
"He didn't tell me anything except that he wants to spar.
"If he wanted to come back, he could. Why not? Everybody would watch. It would be huge no matter who he fights. I'm all for it.
"I would love to see Mayweather vs Manny Pacquiao again."
It has been a bad year for Mayweather personally. He has suffered two bereavements - Roger Mayweather, his uncle and the trainer who led him through his heyday; and Josie Harris, his ex-partner and mother of his children.
Boxing, as you would expect, has been his salvation. Mayweather declared "I will be one of the world's best trainers" to honour uncle Roger and duly started working with Devin Haney, the 21-year-old prodigy who holds the WBC lightweight championship.
"He wants to give back to the community because he lost his uncle," Douglin said. "He wants to give back more. He is a very giving person.
"People don't understand how much he gives back because it isn't in the news. People only see him shopping.
"Me for example - he helped me financially. He does a lot that isn't spoken about."
The clearest example was Mayweather's offer to pay for the funeral of George Floyd, the African-American who died in police custody earlier this year. In 2011 he paid for the funerals of his former opponent Genaro Hernandez and the heavyweight legend Joe Frazier.
"Because George Floyd was such big news, [his gesture] got out there," Douglin said. "But Floyd does stuff like that a lot and it's not spoken about. He takes care of a lot of people."
Ashley Theophane added: "Being around Floyd inside and outside the ring is motivational and inspiring, because you see a man that came from nothing and he's made a lot of money. He gives a lot of money away to charities, helps his friends and family. He bought me a car. Mayweather does a lot of good outside the ring that never gets mentioned, because he never says anything."
You sense the door to boxing may never completely close, because he isn't willing to shut it himself.
Those days and nights in the gym won't end anytime soon meaning no boxer in Vegas can sleep soundly without the phone call coming: 'Come to the gym, I want to spar'.