Former All Blacks assistant coach and Crusaders mentor Robbie Deans believes there are only two teams who know they can win the Rugby World Cup – the All Blacks and the Springboks.

Writing in his column for the French Rugby Hebdo newspaper, Deans said: "There are about eight or 10 contenders who are trying to convince themselves they can win the World Cup, but there are only two who know they really can win it: New Zealand and South Africa."

While Deans singled out the All Blacks as obvious favourites to lift the Webb Ellis Cup, he said the Springboks were by far the biggest chance to spoil New Zealand's long awaited party.

"I am sure they have the potential to play at a higher degree of intensity no matter who their adversaries are, except perhaps for South Africa," wrote Deans of the All Blacks.

Deans says there are three reasons why the Springboks may win their second World Cup title.

"The first is historic. And it is not only because the core of the squad is from the Under-21 side, coached by a certain Jake White, that became (Under-21) world champions in 2002 by dominating the final against a New Zealand team that included five players who are here in France, including Daniel Carter," he said.

"These Boks have since notched up some considerable success, like the Tri Nations victory in 2004 or that of the South African sides in this year's Super 14.

"White has at his disposal a mature squad that prides itself on considerable confidence, which is based as much on their performances as the depth of their bench, which has been markedly superior to whatever his predecessors had.

"Victory could be the culmination of some of their careers, for players like John Smit or Victor Matfield ... not to mention (coach) White," Deans wrote.

"South African teams always fall back on their physical prowess and a mentality that is unfailing, but White has added certain mental flexibility," he said.

"Smit is not only a respected captain. He is also a man who can keep his emotions buried deep inside when faced with the pressure moments," he said.

"They are trump cards which could prove to be decisive in the weeks to come.