At one time, Kevin Mitchell was on top lightweight contender who nearing the point of a world title shot.

But everything came crashing down when he was stopped in three rounds by Michael Katsidis, when they battled for the interim-WBO title in 2010.

Mitchell would get a world title shot two years later, and was stopped by Ricky Burns, but many observers felt Mitchell was never the same fighter after suffering that first defeat.

On Saturday night, Mitchell watched a friend of his, Anthony Joshua, suffer the first defeat of his pro career.

Joshua made his United States debut at Madison Square Garden in New York City, and he was dropped four times, and eventually stopped in the seventh, by massive underdog Andy Ruiz.

Ruiz walked away with the WBA, IBO, WBO, IBF heavyweight titles.

The outcome is regarded as one of the biggest upsets in heavyweight boxing history.

In the aftermath, Mitchell explains that now Joshua will have to rebuild his mental state.

"[Joshua] looked in a bit of a daze [after the fight]," Mitchell told Love Sport Radio.

"This is what people don’t see in boxing now, the mornings where you wake up on your own, you don’t have your belts, all the money in the world can’t help you in your down days. Nobody sees that. They think it’s a great life, they see you driving a nice car and living in the big house, flying on private jets, but newspapers that have been praising you for years are now showing you on your a***. He’ll be in a very dark place.

"That’s boxing - one minute you’re the best thing in the world, next thing you’re chinny. Any heavyweight that gets hit with a good shot is going over. What we’ve got to look forward to now is how he’s gonna return. Give him a few weeks to clear his head and he’ll be back in the gym very determined.

 "Last thing I said to [Joshua] was 'keep your hands up and don’t think this is gonna be an easy fight'. I’ve been there before and I’ve had a few slip-ups in my career in big fights and you think you’re better than what you are. I don’t think that’s the point with AJ though. He’s a heavyweight and any heavyweight that gets hit can be hurt. After his (Ruiz) first few shots, he felt his power. I think he went in there with the wrong tactics, thinking he was going to blow him out, I think we all did. "What matters now is how he’s going to come back, how he’ll return for the fight. That’s the sign of a great heavyweight, if he can come back, win the belts back and move onto the Furys, the Wilders."