The closer Anthony Joshua gets to boxing greatness, the more the sport's new superstar is driven by a fear of failure.

"I just know how quickly the tables can turn," the 28-year-old Englishman said in one of the more candid moments of his build-up to Saturday's heavyweight unification fight against Joseph Parker in Cardiff.

"One minute you're the man, and the next you're not."

Parker represents a big threat to Joshua's seemingly unstoppable rise to the status of undisputed champion of boxing's most glamorous division.

The 26-year-old New Zealander has never been knocked to the canvas in a 24-fight professional career and, like his opponent, is unbeaten.

Then there's the revelation, made last week, that Parker has been fighting for the past two years with a debilitating elbow injury that prevented him from executing his jab in three title fights.

After two surgeries late last year, he is fully fit and likely to be a different fighter to the one Joshua will have seen in video clips.

And there's his heritage. A New Zealander of Samoan descent, Parker first began thumping a punch bag aged 4 under the gaze of father Dempsey -- named after Jack Dempsey, the American heavyweight champion from 1919-26 -- and emerged from an impressive amateur career with fast hands, a warrior spirit and, now, the WBO belt.

Joshua -- the WBA and IBF titleholder with a 20-0 record (20 KOs) -- has been the epitome of cool, to the point of arrogance, some say, over the last few weeks but he knows he is in for a real fight.

So does his promoter, who has one eye on an even bigger bout -- against American Deontay Wilder -- later this year.

"That's the biggest fight in world boxing," Eddie Hearn said of Joshua-Wilder. "But I honestly see this fight a tougher fight than Wilder. Not necessarily more dangerous but just a tougher all-round fight, technically. I'm nervous for the fight and I know AJ's mind is completely on Joseph Parker."

The defining fight for Joshua so far was the epic victory over former champion Wladimir Klitschko in front of 90,000 spectators at Wembley Stadium in April last year.

He was already a huge name at home but that win grabbed the attention of the world -- and ended Klitschko's career.

Having successfully defended his belts with a 10th-round stoppage of Carlos Takam in front of 77,000 in Cardiff's Principality Stadium in October, Joshua has been taking advice from Klitschko's trainer ahead of his return to the Welsh capital.

"I'm finding ways to improve and new ways to get better," Joshua said. "I chat to Johnathon Banks a lot, a friendship which developed from when I trained with Klitschko as a sparring partner. I use the conversations as a way to speak to Klitschko.

"'How did he forever want to improve?' -- I ask these questions. He told me they worked a lot on his jab and his movement before the fight with me. It's humbling to know that he got beat a few times and managed to come back."

Again, there was Joshua raising the prospect of losing.

The two fighters met for their final head-to-head news conference on Tuesday, Joshua looking athletic in his tracksuit and T-shirt while Parker turned up in a sharp suit, tie and glasses. He looked more a professor than a boxer.

"He was brought up to dress the best and wear himself well, be clean-cut," Parker's mother, Sala, told The Associated Press in a recent interview. "That's how he was growing up.

"He cannot trash-talk because he was never like that. It's hard for him to change his person. We've tried to retain his values as a good person."

Sala and Dempsey will be there in Cardiff, as will Wilder, for a fight that could turn Parker into a household name or leave him as another boxer Joshua tramples over on the path to becoming the first undisputed heavyweight champion since Lennox Lewis in 2000.

"He's someone who will add something to my life journey," Joshua said.

The Englishman's power is undisputed -- Parker's less so, particularly in light of his elbow issues -- and Joshua is learning to control fights behind his jab and reach, which will be 4 inches longer than his opponent's.

Joshua is also now a bona fide "stadium fighter," so much more used to the big occasion than Parker, and a near-80,000 crowd is expected under the roof of Wales' national stadium.

"He's a phenomenon," Hearn said. "It's not like we can rock up and do Wembley next week with another fighter: That's just with Anthony Joshua. We are lucky to have him in our sport."


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