By Liam Napier

David Haye is an optimist, a boxer who subscribes to the philosophy of cometh the hour, cometh the man.

The renowned former British heavyweight champion reckons it is now or never for Shane Cameron. And rightly so.

Seven hostile London-based sparring sessions gave Haye an insight into Cameron's burning motivation to exorcise his David Tua-inflicted demons. Haye dished out punishing blows, accompanied by some pertinent advice, and was impressed by Cameron's retaliation.

"No-one was knocked down but it was no-holds-barred sparring," Haye told the Sunday-Star Times from London.

"It was guns blazing from the first day. That's exactly what we wanted and exactly what Shane needed. We did some great rounds. It was mutually beneficial, him travelling halfway across the world."

Cameron's lingering scars from the Tua demolition are bone-deep. The beating he took in his last meaningful heavyweight scrap nearly three years ago was demoralising. Yet that was only his second defeat.

His challenging task against Monte Barrett in Auckland on Thursday could be Cameron's final chance to make amends. To prove he can step up in class. Prove he doesn't freeze on big occasions. Prove he is not out of his depth and that he is better than his record suggests.

In the context of Cameron's career, the importance of this fight cannot be understated. Retirement may beckon with another underwhelming loss.

"Personally, for myself, I have to make a statement," he said. "And for the nation. I want to bring those [WBO Asia Pacific and Oriental] titles back to New Zealand."

With that desire, Cameron ventured to England for a taxing two and a half week training camp with Haye, accepting the fatigue risks, given he had just seven days to overcome jetlag before his career-defining moment.

"It's going to be a disaster for him," Barrett claims.

"David Haye can't put the gloves on for him. He can't dodge punches. I hope Shane has something left for me. David Haye is a beast. He wouldn't have been taking it lightly on Shane. I'm still going to beat him, even after he went over there and got all that experience."

After his up-close viewing, Haye disagrees. He, instead, believes Cameron's speed and do-or-die mentality will be enough to shock the trash-talking American.

"I believe Shane, being the underdog, that will work in his favour. He's got no pressure. He's got everything to gain and nothing to lose," Haye said.

"He's training like a guy who has got a huge point to prove. There's a lot of people writing him off. That's why he came over here. To dedicate himself to the cause. He's gone above and beyond the call of duty for this fight."

Having gone toe-to-toe with Cameron, and recording a brutal fifth-round victory over Barrett in 2008, which included five knockdowns, Haye is perfectly placed to assess the two fighters.

"I know Monte Barrett pretty well. I've been giving Shane some tips about what to utilise in his fight," Haye said.

"Just in case Monte is reading, I don't want to give too much away. All I'll say is if Shane does what he's been doing in the gym here, he will be the victor. When I fought Monte I was the better fighter and I believe Shane will also reign supreme. He's in fantastic condition."

Insiders feel Cameron's main weakness is bravery, with his tendency to walk forward into punches resulting in a battering. Barrett, the only man to floor Tua, possesses a powerful punch and could expose this trait.

"Defence is going to be an important factor in this fight so we've been making sure our chins are tucked down and hands are up," said Haye, who is preparing for his grudge fight with Dereck Chisora.