Dereck Chisora 31-9 (22) believes his next opponent Joseph Parker 26-2 (20) has lost his hunger for the game since relocating to Las Vegas.
The heavyweights will clash in an important crossroads bout at the O2 Arena in London on October 26.
“The guy is good. He has a good right hand. But I believe that, since he moved to Vegas, he doesn’t have hunger,” Chisora told Soccer AM.
“That’s massive in the game.
“I’ve got some losses but I’m gassed and pumped for the fight.”
Former WBO champion Parker is the only man to defeat IBF, WBA and WBO champion Andy Ruiz Jr, who shocked the world by knocking out Anthony Joshua in June.
The 27-year-old Kiwi has scored back-to-back knockouts after losing a pair of decisions to Anthony Joshua and Dillian Whyte in Britain last year.
Chisora, 35, who is coming off a second knockout of Artur Szpilka, said he doesn’t rate Parker as a fighter.
“One out of 10,” he said.
“I like the guy. He’s a family man, a cool guy. I shook his hand.
“But after I released my hand, we’re at war.
“There’s no playing around anymore.”
Meanwhile, Parker’s trainer Kevin Barry told Sky Sports that they have been using rough and ready sparring partners as they expect Chisora to employ dirty tactics in the fight.
“Everything from leading with his head, using his elbows, and his forearms and low blows, and choking Joe with his arm, pushing Joe’s head down,” Barry said.
“All the fouls that we know Derek Chisora has as part of his skill-set.”
Parker’s promoter David Higgins is calling on the officials will play an important role in ensuring it is a fair fight.
“Joseph Parker and Kevin Barry are 100 per cent right to be gravely concerned,” said Higgins.
“We’ve got a 100 per cent rate of unfair treatment in the UK by the officials. I invite the British public and media just to look at the tapes, you can see it. It’s not opinion, it’s fact.
“We would call for a level playing field, and we’ll be scrutinising very closely the choice of referee, in particular, as well as the judges too. The referee has been the main issue for the three fights, rather than the judges.”