Joseph Parker is confident of causing a major boxing upset over Anthony Joshua as he believes he has not had the chance to display his full range of skills.

Parker will put his WBO heavyweight title and unbeaten record on the line against WBA, IBF and IBO champion Joshua, also undefeated, in a title unification fight in Cardiff on 31 March.

Fans, pundits and fellow boxers are all backing "AJ" as the favourite but the New Zealander believes he will not only inflict Joshua's first-ever defeat, but is capable of knocking him out in the process.

"I can outbox Anthony Joshua. I think I have the skills to outbox him but I haven't really shown that," Parker said, as quoted on RadioNZ. "That's why I'm excited - this is a big stage to put on the best performance of my life.

"I can knock him out. I can outbox him. Words can't explain how excited we are. We're fighting in his backyard and we're fighting another champion who's undefeated. That makes it a great fight."

Parker's trainer Kevin Barry recently claimed the 26-year-old was in better shape for Joshua than he was for his last title defence against Hughie Fury back in September of last year.

And with less than a month to go for the big clash, he remains confident of a win for Parker.

"He wins the fight with speed and movement," Barry explained. "He wins the fight with a higher level of skill. Parker has far better skill than Anthony Joshua. He has a far better selection of punches. He is very durable.

"If the best Joseph Parker turns up, we will leave the ring with all the belts."

Dillian Whyte, who notably lost his unbeaten record to Joshua back in December 2015, recently claimed the fight at the Principality Stadium would get to Parker.

But Barry retorted that it will play no role even if it will be the biggest crowd the South Auckland native will have fought in front of.

"It won't matter if there's 800, 8,000 or 80,000 people at this fight," Barry added. "It will be the same Joseph Parker that walks to the ring. I'm not one bit worried about the occasion getting to him."