A boxer who has fought both Anthony Joshua and Joseph Parker is predicting a convincing win to the big Brit in their heavyweight world title fight.

Frazer Clarke is the common denominator to the two champions seeking to unify three of the heavyweight division's four main belts when they fight in Cardiff on March 31.

Clarke fought both Parker and Joshua in the amateur ranks and the 26-year-old has resisted turning pro, trying to fulfil his Olympic dream at Tokyo 2020.

GETTY IMAGES British boxer Frazer Clarke predicts Anthony Joshua will have an easier win against Joseph Parker than his 10th round TKO of Carlos Takam.

Clarke lost to both Parker and Joshua in 2010 – "Parker nicked it off me" - and has gone on to help IBF and WBA champion Joshua with sparring.

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GETTY IMAGES WBC champion Deontay Wilder gives Joseph Parker a decent chance against Anthony Joshua but feels the Kiwi will need a knockout to win.

He believes Joshua has too much size and power for Parker, the WBO champion.

"I think Joshua wins really convincingly. That"s not bias, that's just honest opinion," Frazer told Boxing News.

"I think Joseph Parker is good [but] I know Joshua is in great condition. He's in better condition now than he's been going into any camp. That's 100 per cent the truth."

"I think it starts off a little bit cautious. I think Joshua takes him out inside four or five rounds. I think it's an easier fight than [Carlos] Takam, I don't think he's as durable," he added, seeming to forget Parker outlasted Takam for a 12-round points win in Auckland in 2016.

Clarke also felt Parker lacked genuine size for this assignment.

"Parker's quite good at attacking but I think he's small for a heavyweight as well. I've stood next to him at the Hughie Fury fight and weigh-in and stuff. I think Joshua is going to tower over him, do an absolute job and look good doing it."

Frazer doubted Parker's noted chin could stand the power of Joshua.

"Let me tell you now, there's having an iron chin and then there's getting hit by a combination off Anthony Joshua. Not one punch, his one-punch, concussive knockout power – he has got that but we haven't really seen that too often – but what I'm telling you is after Joshua's hit you four or five times on the chin, it hurts any man in the world, I don't care who you are. His chin will well and truly be tested let's put it that way."

Taking training to new depths💧 A post shared by Anthony Joshua (@anthony_joshua) on Jan 24, 2018 at 5:09am PST

Meanwhile, outspoken WBC champion Deontay Wilder, who is hoping to face the winner of Joshua v Parker, continued to offer his thoughts on the Cardiff showdown. He gives Parker a strong chance but believes he will need to deliver a knockout to win.

"You know, I wish Parker all the best but I think Parker is definitely gonna have to knock Joshua out to win that fight," Wilder, who defends his belt against Cuban Luis Ortiz in New York on March 3, told Fight Hub TV.

"I see that fight going late rounds. Whatever happens I feel like it's gonna happen in the late rounds, and I definitely give Parker a chance...

"We always hear 'the heavyweight division, everyone can hit, blah blah blah,' which that ain't true. Just because you a heavyweight that don't mean you can hit because, honestly, some guys can't even kill a fly on the mitts if they tried. So that don't mean nothin'. But it's all about what's up in [your heart]. And I feel Joseph Parker is coming, he got the heart, we'll see what happens but I think he's definitely gonna have to knock him out to win that one."