The All Blacks didn't just put their foot on a French throat in Cardiff, they slammed it on the accelerator.

The key to that was the firepower on their bench, and that's where New Zealand are far superior to other World Cup contenders.

South Africa have a bit of spark in reserve for the semifinal. They can bring on a player like hooker Adriaan Strauss who is like a loose forward, but don't possess anything like the impact players the All Blacks have.

You could sense the French body language as the All Black substitutes came on. It must be so demoralising for opponents. Every time the referee blew his whistle, the French would look over to see another game-changer arrive.

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It was a conveyer belt of heavy artillery: big Charlie Faumuina and his ball-playing, an athlete like Victor Vito, then Sonny Bill Williams sets up tries, Sam Cane gets three turnovers in 10 minutes, Beauden Barrett helped set up tries, Tawera Kerr-Barlow scored tries, even the veteran Keven Mealamu made a significant contribution.

Other teams can maintain momentum but the All Blacks increase it. It's not always easy making your presence felt off the bench, believe me - I've been there. But the All Blacks are perfecting the art, and it's hard to recall a substitution shocker in the past four years.

Apart from the odd exception, mainly at halfback, they give replacements time to have an influence rather than making the token gestures of old, even when the outgoing player has been performing well.

There has been significant evolution in the way New Zealand uses their replacements. Opponents must look at what is going on and think, 'this is ridiculous. How can we stop the bleeding?'

What about the Springboks? They need to play a less confrontational game and get players like Duane Vermeulen, Francois Louw and Lood de Jager operating wider than just in the 10m channel next to the rucks.

A few years ago, Vermeulen was offloading like Kieran Read can - one or two in from the wing - and it caused New Zealand all sorts of problems.

They also seem a bit vulnerable in contact. I noticed Bismarck du Plessis caught running too high. He is so strong he could stand in the tackle and throw the ball back, but that's not the type of contact you need for multi-phase rugby.

Do I think they can tip over the All Blacks? History says no outside of Ellis Park and South Africa.

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My biggest concern for them is that when they play with that dour mindset, it is the Springboks who actually run out of puff.

These sudden-death games are won on big moments - they will have their share and have enough experience to take their chances - but I believe they will need a decent lead going into the final quarter.

They need to move the All Blacks around, as they do at Ellis Park. I don't know why they play differently in Johannesburg. Maybe they feel the All Blacks can be run out of oxygen on the high veldt. Whatever the reason, it causes the All Blacks problems and they look a different beast there.

Unless injury dictates otherwise, they should stick with de Jager in the starters, at the expense of the veteran lineout ace Victor Matfield. The Springboks need de Jager's robust presence, and I would have Matfield on the bench in case things go pear shaped in the lineout.

In the other semifinal, Argentina have every chance of beating Australia. The Wallabies should have the best player at this tournament, David Pocock, back from injury and they didn't look the same without him against Scotland. But game management is just one area where the Pumas have vastly improved. They are not mugs anymore and know how to win big games.