Anthony Joshua has warned Andy Ruiz and any other ‘little f***** ’ who wants his belts that he is fresher than ever as he prepares to make his US debut.

The WBA, WBO, IBF and IBO heavyweight champ takes on the Mexican American in New York’s Madison Square Garden on Saturday in what will be his first fight since defeating Alexander Povetkin at Wembley Stadium nine months ago.

He said: “The time out is a good thing, I needed it, I am fresh now.

“I know how to fight. Give me five years out of the ring and I could still come back.

Joshua is ready to make his US debut (
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Getty Images)

“Look at Tyson Fury , he took three years out. Once you know how to do it, you know how to do it.

“I am at a stage where fights are tough, you get a bit of rust, but nothing a bit of WD40 and polish can’t get sparkling again for June 1.

“I have had time to do things for myself, I have improved my diet and I told the team I never wanted to become complacent because, even if it’s not today, then some little f***** is going to come up and give me a run for my money.

“Nine months of research will help me with the next five years of boxing.”

Ruiz stepped in after Joshua’s original opponent, Jarrell Miller, tested positive for three different drugs with three different anti-doping agencies.

Contender Ruiz in training ahead of the big fight (
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Joshua added: “You can’t underestimate any heavyweight so I don’t take Andy lightly.

“He has shown he has heart, he can fight, he can box and that’s what matters.

“He will bring it and it’s my duty to beat him.

“I will look to break him down one round at a time.

“It might not be round one, but my main aim is to put on a spectacular show for the fans.”

Providing AJ does deal with Ruiz, then the focus will return to making a fight with WBC heavyweight champion Deontay Wilder to see which one of them is the undisputed king of the big boys’ division.

Fans are desperate to see Wilder become Joshua's next opponent (
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SIPA USA/PA Images)

The American’s co-manager, Shelly Finkel, said on Friday that Wilder’s next three fights will be against Joshua, Fury and Luis Ortiz.

Joshua said: “No, I’m not getting sick of talking about Wilder and Fury — we are in the same era, the same time, the same division, we have the same goals and these fights have to happen.

“Rivalries are really important and fighters in the same era have to fight each other.

“But the focus has to be making the fight in the first place.

Joshua will be the hot favourite against Ruiz (
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PA)

“I am not looking past Ruiz, though, I need to deal with him and then we will look at what happens next.

“I need to create my own lane and my own legacy.

“I need to beat Ruiz and then I can start thinking about that.

“I have made it very clear that I am on the road to undisputed, God willing I come through Saturday with the ‘W’ and then we want Wilder.”