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Ferdinand spoke to Joshua ahead of his WBO, IBF and WBA heavyweight title defences against Oleksandr Usyk on Saturday evening.
Joshua asked the former England international, on William Hill's YouTube channel, what he could do to reach the elite levels Ronaldo does aged 36.
He replied: "I think you've gotta be brave - people never talk about Cristiano's bravery.
"He was brave to take risks, he came over to another country. He was brave to remain the person that he was, and didn't change really.
"He became obsessed with the sport that he chose and then drilled down into details which was building a team around himself.
"I went round his house one time and I walked in and he had about six/seven people siting in his front room. I said to him, 'Cris, who are all these people, man?'
"He was like, 'That's my personal masseur, my nutritionist, my doctor, my physio, my chef.'
"He had all these people and back then no one was doing that. He was a visionary in that sense.
"He's just looking for every little detail that's going to enable him to improve.
"He'll send me a picture and he's doing deep water recovery sessions in the sea. He's driven two hours to get there when he was in Turin with Juventus.
"Other people are at home or out at dinner. He's just looking for that extra edge."
Ronaldo takes a number of steps to maintain his remarkable physique.
One of those is an irregular sleep schedule, with Ronaldo sleeping up to five times a day for two hours a piece.
Another is his diet, said to be strictly organic and rich in nutrition.
Ferdinand played with Ronaldo for six years before the five-time Ballon d'Or winner sealed an £80 million move to Real Madrid.
He thinks the Portugal international will always be the best player he ever played with.
Ferdinand continued: "Obviously Cristiano is just ridiculous.
"When he joined us he was a baby, but his intelligence to grow, his obsession to get better and his desire to be the best was just relentless.
"I've never seen anything like it, just a man possessed to get to the top and would do anything to get there."
Featured Image Credit: William Hill/YouTube, PA Images & Cristiano Ronaldo/Instagram
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