Hang on to your hats, cross your fingers, dig out your good luck charms and say a little prayer — this one's going to be very close indeed!
Just about everybody in Japan and around the rugby world have been lavish in praise of England after the New Zealand game and seem to have already anointed Eddie Jones's team as world champions.
That really worries me. Sport just doesn't work like that. In a knockout tournament, your last game counts for nothing.
England have to find the energy to go again after emptying the tank against New Zealand
It counted for nothing in 1987 when France recorded a memorable semi-final win over Australia only to misfire badly a week later in the final against New Zealand.
It was irrelevant in 1995 when New Zealand thrashed England only to lose to South Africa. And in 1999 it was exactly the same when the French again produced rugby from the Gods against the All Blacks only to implode a week later against Australia.
Eddie knows this better than anybody. His Aussie team produced a memorable semi-final against the All Blacks in 2003 only to lose to us a week later.
I enjoyed the little verbal spat between Eddie and Warren Gatland this week on this very subject, and the truth is Warren was right in what he warned.
He might well have done England a favour by emphasising that, ultimately, semi-finals count for nothing unless you win the final.
This is not going to be a walk in the park — in fact it's going to be an incredible dogfight. South Africa are a hugely strong and highly motivated side, the Rugby Championship holders. They're a side with a massive game in them and if not now, when?
They will also be ready and waiting for England. There is no question in my mind that England caught New Zealand a little on the hop last week.
Eddie Jones understands that South Africa will know his players better than the All Blacks
The two sides had only met once in the previous five years and England had developed massively after that game, in November 2018. England's pace, physicality and skill levels surprised New Zealand. But none of that will surprise South Africa.
Vincent Koch, Faf de Klerk, Franco Mostert, Francois Louw, Schalk Brits, Cobus Reinach and Willie le Roux know all about English rugby and our top players from their time in the Premiership, while another tranche of Boks play in the French Top 14 and regularly meet top English clubs in the European Cup.
The Kiwis, with all their players having to be based at home, didn't have that recent experience of how quickly the top England players have developed over the last year.
I was struck by how together the Boks looked in footage of their last squad session on Wednesday when Brits, who retires after this World Cup, addressed the group.
And, of course, with Siya Kilosi as captain they are on the verge of another incredible story that transcends rugby, a black South African captaining his country to a World Cup triumph.
The other thing to remember about the Boks is that they are the masters of doing what it takes. They have played in two World Cup finals, won two and are yet to score a try.
The Springboks traditionally know how to win a tight game, especially in a World Cup final
They won't be remotely concerned if they win 3-0 or 6-5. They will feel under no pressure to entertain or contribute to a fine spectacle. And rightly so.
I have been chatting with John Smit and Bryan Habana this week and they will happily concede that the 2007 World Cup final in Paris was one of the worst Test matches they were ever involved in.
But it mattered not a jot because they did exactly what needed to be done to subdue a powerful England pack and took the William Webb Ellis Cup back to South Africa.
The Boks know that is their best chance of beating England again this time around and again we see they have picked six forwards on the bench — the so-called 'bomb squad' — and they are all major players.
If the game is level after 60 minutes when that lot come on, I'm going to be very