Amir Khan has issued a warning to heavyweight Anthony Joshua - by advising his countryman to step away from a potential rematch with Andy Ruiz.

Last Saturday night at Madison Square Garden in New York City, Ruiz pulled off a massive upset when he stopped Joshua in seven rounds to capture the IBF, IBO, WBO, WBA world titles.

Joshua was dropped four times before the contest was waved off by the referee.

Joshua has already exercised an immediate rematch clause, and the second fight is being targeted for the fall.

But Khan would advise Joshua to take one or two tune-up fights before facing Ruiz for a second time.

He's actually shocked that promoter Eddie Hearn would allow Joshua to face Ruiz in back to back fights.

"When I heard he was doing that I thought it was the worst mistake he could make,” Khan said to Declan Taylor. “Look, first of all, Ruiz will be full of confidence going into this fight and you’ve got Joshua who will be a little bit on the edge and on the back foot knowing that he can be hurt and put down.

“I think it’s a very bad to take back-to-back and I can’t believe Eddie is putting him straight back into the mix with him. I think he needs a nice easy knockout win – maybe two – and then have the rematch.

“Joshua seemed to be quite chilled and he came across well after the fight but mentally you are upset. It kills you, to bits. You might not show that – you might be so straight-faced and strong that you might not show it. But deep down, he must be in bits, definitely.

“He was the heavyweight champion but I bet he cried that night. When you’ve lost all them titles it’s like you’ve lost your babies. With me, I lost friends. Friends who were big supporters of mine turned around and said I was finished. People stop answering your calls, the big contracts leave you. I had contracts with Reebok, who were paying me a lot of money, and they just washed their hands of me. They said ‘see ya later’.

“Mate, it happens too quickly. That’s why boxing is the hardest and most brutal sport. If you lose in boxing they throw you under the bus. Even though you’re more upset than they could ever be, they are the cherry on top by taking things away from you. Then people talk shit about you. Anthony will tell you himself, it’s a very dark place when you get beat. It doesn’t make it easier when your friends desert you and only a handful of people stay with you. I saw it after the Canelo fight. When I lost that Canelo fight a lot of my team left me, a lot of my friends left me. I had to rebuild myself.”