Former New Zealand star Sean Fitzpatrick believes South Africa will need "the game of their lives" to beat England in the Rugby World Cup final.
The Springboks defeated Wales to book their place in Saturday's showpiece where they will play a rematch of the 2007 final.
This match comes after England sensationally upset the All Blacks, who were two-time defending champions, the world's top-ranked side and tournament favourites.
Fitzpatrick, who watched that stunning All Blacks loss at close quarters, claims a South Africa victory would be similar in magnitude to England's win, having been hugely impressed by the squad Eddie Jones has built.
"[Jones] is a wily old character and he's got huge experience. He'll be doing everything he can," Fitzpatrick said, speaking courtesy of Laureus. "He's had a four-year plan, he's developed a squad that's very deep and a squad that will want to win the World Cup.
"I said last week, it's going to take a heck of a performance to beat the All Blacks but, if they do, they'd deserve to be there.
"This week, the roles are reversed. If South Africa beat England, they are going to have to play the game of their lives. I just can't see England losing at the moment."
If the Springboks are to triumph, 1987 World Cup winner Fitzpatrick suggests England would need to turn in an error-strewn performance, having previously profited from the All Blacks' mistakes.
"It'll be the team that makes the least mistakes," he said. "We saw an All Blacks team that made more mistakes on Saturday than they had in their previous games.
"If you make mistakes, the opposition at this level are teams that are capable of capitalising on those mistakes.
"They both have got a burning desire to win the World Cup but, for me, it's literally as easy as that. You make the least mistakes and you'll win."
While impressed by England, Fitzpatrick is now intrigued to see how they now handle playing as favourites, having also moved to the top of the rankings.
The 92-cap international said: "The biggest thing for me this Saturday is to see how England react to the pressure of being favourites, being number one in the world, up against a team not a lot of people think can beat them."