Promoter Eddie Hearn is backing Anthony Joshua to "finish it inside six rounds" when he fights Joseph Parker in Cardiff tomorrow.

British heavyweight star Joshua, 28, will put his WBA and IBF titles on the line against WBO champion Parker in front of a capacity Principality Stadium crowd.

It will be the Watford star's sixth world title fight in only his 21st professional bout, and he is widely expected to claim another notable victory.

"I thought this fight was going to go late," Hearn said when the show's undercard fighters were presented to the media.

"But I have got a funny feeling seeing Joshua and his edge this week, that he is going to finish it inside six rounds.

"It's a massive fight for AJ, and it's high pressure.

"Of course, he has got this reputation of being a massive star, but he is still learning, and to be in these kind of fights this dangerous this early in his career, he's a little bit edgy.

"He is ready to fight, and he knows how tough a fight it is. He is ready, he is looking in great shape and I think ready to add another belt to the collection."

American Deontay Wilder is a potential opponent for Joshua further down the line, and Hearn admitted that "it is important to get him in the ring at some stage," but all attention is currently concentrated on the challenge posed by unbeaten New Zealander Parker.

"People don't realise that he (Joshua) is moving so quickly," Hearn added.

"He will give them (the public) every fight they want, they just have to stay patient and follow the journey, and hopefully for many years to come.

"The only danger is that he does it all before he is ready.

"As a heavyweight, I think he wants to go on to his mid-30s, so we want to take it at the right pace, but at the same time we have to listen to the demand of the fans and know that he wants to give them what they want, not just our broadcasters."

Joshua has captured the British public's imagination after following up his London 2012 Olympic gold medal by stopping all 20 of his opponents in the paid ranks, and the Parker bout will be his third successive stadium fight, with a crowd of around 75,000 expected.