The Irish presence in Paris has been picking up over the last few days and this is a game Ireland have been gearing up for since they beat England on 18 March to win the Grand Slam.
Everything since then has been geared towards this game against South Africa. It's a massive game in so many ways even though there is a little bit of a get-out clause, if you manage to lose it, given that we have Scotland in two weeks' time.
But that said, this is the one you want to win. South Africa the reigning champions, you have number one versus number two in the world - it's a game fit for the final itself.
The Springboks have always had massively powerful forwards but they have actually allied that with some incredibly skillful backs.
I think they are a more balanced side now than when they won the World Cup four years ago. They certainly have more of an attacking threat.
But that said, the power is up front. The talk all week has been the unprecedented scenario in a World Cup where you have seven forwards and only one back on the bench.
I think Jacques Nienaber and Rassie Erasmus announced the South African team two days early. The regulations are you must name the side two days before the World Cup game. They named it last Tuesday and it was almost throwing the gauntlet down to Ireland: 'Look, this is what we're bringing.'"
There was a suspicion that they might go down this route when they did it for the very first time against New Zealand in a warm-up game in August.
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But Ireland haven't blinked and that's the whole thing. Andy Farrell has his tried and trusted formula.
He's picked his strongest team but he has stayed with five forwards on the bench. As a consequence, when you play South Africa, it really becomes a 23-man game.
Everybody has to make a massive contribution and the game is normally decided in the last 15 minutes because of the attrition level that you face.
In eight of the last 11 games, it's been decided by six points or less, so it's going to be incredibly tight.
It's so tight to call but I fancy Ireland. I think they have geared everything towards this. For South Africa, I think Malcolm Marx is a massive loss to them.
There is also a question mark about Mannie Libbock at out-half. He's inexperienced and they have brought Handre Pollard back into the squad which can't be a huge boost of confidence for Libbock.
They brought an out-half in to cover an injured hooker. So I think we might just have enough to get over the line but it might be a prelude to meeting them again later in the tournament. It could only happen in the final I think. But I give Ireland a slight edge.
Donal Lenihan was speaking on RTÉ Radio 1's Morning Ireland.
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