Anthony Joshua proved critics wrong who accused him of quitting – new documentary AJ: Fighting Back tells the tale

"I think that he quit."

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Andy Ruiz Jr was looking Anthony Joshua square in the eyes when he made the dreaded accusation that would ultimately be proved wrong in their rematch.

AJ: Fighting Back is a new Sky Sports documentary, available On Demand now, that shows never-before-seen footage of Joshua's redemption in his second fight with Ruiz Jr.

Recovering from his shock loss to Ruiz Jr in New York was an emotional, soul-searching experience for Joshua who won back his IBF, WBA and WBO heavyweight titles in the rematch.

Within touching distance of an undisputed title fight against Tyson Fury, it feels like a long time since Joshua's willpower was questioned. But heading into his rematch with Ruiz Jr he was forced to endure probing claims.

"I thought he quit because of the way it was going," Ruiz Jr said. "He was out of it. He didn't know where he was, in that moment. I think that he quit."

Deontay Wilder piled into the furore: "He got knocked down four times. He quit, in my opinion."

But Joshua remained steadfast throughout the conspiracy theories that swirled about why he lost the first fight.

Why take the rematch so quickly? "Because I know I can get it back," he answered.

Paulie Malignaggi said: "Going for the immediate rematch tells you that AJ knows he did not quit."

Joshua would gain revenge with a disciplined, skilled performance and AJ: Fighting Back offers an insightful pre-fight clue about his tactics.

"My style is not what a scared fighter does - it's what a smart fighter would do. I will engage to my benefit," he said before carrying out those plans.

"When it comes down to that fire? You've got it or you don't. I've got it.

"I got burned the first time, I won't get burned the second time."

The inner self-belief, Joshua insists, was built in Azerbaijan in 2011 at the world amateur championships when he lost a fight but rebounded to win an Olympic gold medal a year later.

Now as a two-time world heavyweight champion he may be harder to stop than ever.

Will we see a different AJ against Pulev?

"You will see one of the best AJ performances - the shackles are off from the Ruiz Jr 2 fight in terms of being disciplined and following a game-plan," Joshua's promoter Eddie Hearn previously told Sky Sports.

"He can be more destructive in a better stand-up fight.

"The Ruiz Jr defeat taught him not to be influenced by outside noise. Stay focused, look after yourself, be selfish.

"He gave time to everybody but this is an unforgiving sport and you've got to look after No 1. He did that for the Ruiz Jr rematch and he will do it again."

What threat does Pulev pose?

The Bulgarian's only defeat in 29 fights came against Wladimir Klitschko.

He has since beaten Derek Chisora and Hughie Fury.

"Kubrat Pulev is a very good boxer," Hughie's father and trainer Peter Fury previously told Sky Sports. "He learned a lot from the Klitschko fight where he got himself chinned. He's more defensive and he's got a very, very good jab. He's tough, but he doesn't hold a lot of power.

"He's a force to be reckoned with and he won't be easy. It's a good fight. Anything can happen at this level of fights.

"He's a very patient man, Pulev. He doesn't have knockout power, but he's a good boxer, and he's very wise in that ring. He just seems to do enough and control it."

Watch Usyk vs Chisora on Saturday October 31, live on Sky Sports Box Office, from 6pm. Book it via your Sky remote or book it online here. Even if you aren't a Sky TV subscriber you can book and watch it here.