South Africa’s opening Rugby World Cup meltdown against Japan has turned them into tougher, more focused opponents according to All Blacks coach Steve Hansen.

The Springboks are unbeaten since their 34-32 against the Japanese in Brighton on September 19, a result rated among international sport’s great upsets.

The two-time champions were untroubled in subsequent pool wins over Samoa, Scotland and the United States before pipping Wales 23-19 in a tense quarter-final to set up a showdown with New Zealand on Saturday (Sunday AEDT) at Twickenham.

Hansen says it is noticeable how much the Springboks improved following the first game, reckoning they were jolted into action.

“I thought they came under enormous pressure early on in the tournament,” Hansen said.

“Funnily enough, I think, after an initial shock back home, the country has got right behind them. They’ve got great support and they seem to be growing an arm and a leg each week.”

Hansen praised the mental aptitude of the South Africans to create a match-winning try to captain Fourie du Preez over the closing minutes.

The All Blacks were never tested in that fashion, steamrolling France with nine tries in a 62-13 romp.

Meanwhile, Hansen joked that he marvelled at the emotion shown during Tests by Springboks counterpart Heyneke Meyer.

Footage of a worked-up Meyer reacting colourfully in the stands to the highs and lows of South African games is proving popular with broadcasters and on social media.

“I think if I did that I’d probably have a heart attack,” Hansen said.

“I don’t know how he hasn’t had one. He wears his emotion on his sleeve and I reckon that’s great.”

Hansen says while he feels pressure in every Test, he doesn’t think it compares to Meyer, who faces additional tensions.

“Whilst we laugh at Heyneke, he’s under immense pressure. The rules for his selections are totally different to any other country on the planet. There’s a (colour) quota they have and that makes it different.”