Andy Ruiz v Anthony Joshua Venue: Diriyah Arena, Saudi Arabia Date: Saturday, 7 December Coverage: Live BBC Radio 5 Live commentary with live text commentary on the BBC Sport website and app 'One Night: Joshua v Ruiz' - watch documentary which relives one of boxing's greatest upsets on iPlayer here

When Andy Ruiz Jr bought a white Rolls Royce his father was not happy.

"I told him 'Andy, this is your last car, don't buy any more,'" Andres Ruiz recalls.

"I said, if anything, buy a Rolls Royce and rent it out, make money. You can make $30,000 a month on it."

No matter that a car for his mother Felicitas had been the newly crowned heavyweight champion of the world's first purchase after he dethroned Britain's Anthony Joshua in July, or that he has since bought his dad a new truck.

No matter that he had paid $1m cash for a new home. Or that Ruiz will earn more than $10m in Saturday's rematch in Saudi Arabia.

It was the principle.

"Like a father, I told him to stay humble - don't spend the money, invest it in houses," Ruiz Sr tells BBC Sport.

The advice, at least on car purchases, did not stick. The 30-year-old recently bought a Mercedes G550 jeep - a car that sells for over $100,000 - and as cameras filmed him pulling on to his driveway he simply said with a smile, "another one".

Ruiz's new-found celebrity has seen him meet the president of Mexico and be interviewed by Jimmy Kimmel - as well as funding his car habit

If the cars or his lavish California home and its swimming pool are symbolic of a changed life, so too is the increased demand for the Mexican-American fighter.

Ruiz has met the president of Mexico, he has been interviewed by US talk show host Jimmy Kimmel, he has thrown out the first pitch at a Los Angeles Dodgers game and he has been paraded on the back of a convertible Rolls Royce through the city he grew up in.

The man ridiculed for his rotund physique has even started modelling for a menswear brand.

There have been new gold and diamond chains, and in the words of the champion himself, "fun things I always wanted".

But if his father wants evidence that his son can be sensible about finances, Ruiz did dig his heels in when a rematch with Joshua was called. Contractually he was obligated but his refusal to fight in Cardiff and, for a time, Saudi Arabia led to a fairly common boxing solution - money.

"It was a case of how quickly we could stop the rubbish and say 'Andy, you want more money don't you?'" says Joshua's promoter Eddie Hearn.

A father-son bond cemented in childhood

Life has changed out of all recognition since the days when Ruiz worked for his dad, who runs his own property development business.

I'm here to win - Anthony Joshua and Andy Ruiz Jr face the media before their rematch

"He was mixing cement," says Ruiz Sr, who arrived in the US from Mexico aged eight. "I told him 'do you want boxing or to mix cement?'

"He came from a good background. He lived in a nice house. I bought a nice car for him when he was young but I didn't try to give everything to him - he had to work for things."

The bond between the pair is obvious at an open workout in Saudi Arabia.

"He looks up to me," says 58-year-old Ruiz Sr. "I am really close to him. Whatever I told him, he believed."

And there were times in 2017 when that encouragement was key. Ruiz went the full calendar year without fighting and was almost done with the sport.

Fate decreed otherwise. A win over Alexander Dimitrenko paid $200,000 in 2019 and paved the way for him to take on Joshua at short notice when the Briton's scheduled opponent Jarrell Miller failed drug tests.

That win earned him in excess of $5m. He will pocket over double that figure on Saturday.

"He was depressed sometimes not fighting," recalls his father.

Trainer Manny Robles adds: "Boxing is like life. You have ups and downs. It's being strong to not let a situation defeat you. He overcame it and thanks to that here we are today."

'It felt bad - he's my son, that's his weight'

Ruiz's dad got him into boxing as a child but he was also a keen baseball player

Robles gave his fighter time to himself after the 1 June win. Ruiz did take some time away from the sport but then dedicated himself to a three-month training camp for the rematch as he bids to retain the WBA, IBF and WBO belts he won in such stunning fashion.

There is acknowledgement that there are now new distractions, but Robles adds: "Once I get him in the gym I know he is mine and I have control of the situation. That is what happened for this camp."

Perception of the fighter has changed too. His weight is not drastically different from when he first fought Joshua yet he has moved from being regarded as a chubby walkover to a fast-moving threat.

"It felt bad as he's my son, that's his weight," says Ruiz Sr.

"I told people I would bet money on him winning [the first fight] in the seventh round. People were asking why I had such faith. They wouldn't take the bet so I went to the casinos and bet money and won.

"I made a lot of money. I knew he would win.

"His mother and me can see that he is doing better. As a dad I feel so proud that he is doing the things that he wants. Not a lot of boxers make it. It's like winning the lottery."

Some may say Ruiz won the lottery by getting his late shot at Joshua. But no-one can argue he was gifted a win. He took his chance, plain and simple.

If he wins again, mega fights will come his way.

At least one more new car will be on the agenda too of course, just as long as his dad's not looking.