Former world champion Joseph Parker, 29-years-old, believes is career could realistically be over if he takes a loss to Derek Chisora in their upcoming rematch. 

The two rivals will collide on Saturday night at the AO Arena in Manchester.

Back in May, Parker was knocked down in the early moments of the fight, but rallied down the stretch to win a close twelve round split decision.

This time around, he wants to leave no doubt over the outcome.

"I just want to beat him properly this time," Parker told BBC Sport. "If I can't beat Derek then I have to really look at myself and where I go from there.

"I still have a lot to give the sport. When the time comes I will stop but for now I have a lot to give."

The New Zealand star has been riding a five-fight win streak after losing back-to-back fights, by decision, to Anthony Joshua and Dillian Whyte.

Parker realizes that he can't be a "nice guy" as the contest nears.

Chisora will be coming to make a bruising war, because another defeat could potentially send him into retirement.

"I get along with everyone but a lot of times I may have been too nice leading into a fight. That's something me and my team have worked on.," Parker said.

"In the past Chisora has had a reputation of acting up, but he's always been respectful and nice to me. He showed a lot of care for me and family after the first fight, but I don't know if he's trying to trap and lure me in by being so nice."

"There's nothing but respect for Chisora and what he's done in boxing. The people he's fought and his character - he's been a major star. People love to see him fight because he brings war. If he does retire, all the best for him."