South Africa dominated the scrum and the collisions against England and according to Alan Quinlan, that was the only way they could win.
For some teams, the pressure and expectation can get the better of them but as Quinlan said, it actually made the Springboks stronger.
Speaking on Monday's OTB AM, the former Munster forward said they just fed off the pressure.
"I think this is probably the key to it, South Africa had a fear that if they let England play they were going to lose a World Cup final.
"They looked like a team that had two weeks off because they were so energised by the simplicity of what they had to do.
"England had the extra day off and they looked a bit leggy," he said.
As Quinlan well knows, rugby is about the physical battle and if you have an edge over your opponent physically it can change the game.
"South Africa had a real cause –aside from it being the World Cup final– the whole country was behind them and it can just create a different beast inside you.
"England had all the cards as regards the physical power, the finesse and the confidence. They did it against Australia and New Zealand but it was one step too far.
"The one team that can really unsettle you is South Africa and they caught England a little bit by surprise," the former Ireland international stated.
Quinlan felt that once South Africa got on top physically it was a galvanising force for them.
"Defence can become so enjoyable when you know that guys around you are mad for it and they are mad for tackles.
"They just unsettled England physically and on the day, they got the emotion right," Quinlan said.