Justin Marshall says the Boks will run out of gas in their semi-final against the All Blacks because they don't boast the same calibre of substitutes.

Marshall, who played 81 Tests for New Zealand between 1995 and 2005, believes the impact players will be the difference between the arch-rivals in Saturday's semi-final showdown at Twickenham.

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

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

The former scrumhalf believes there needs to be a variation to the game of players like Duane Vermeulen, Francois Louw and Lood de Jager.

'They need to play a less confrontational game and operate wider than just in the 10m channel next to the rucks. A few years ago, Vermeulen was offloading like Kieran Read – one or two in from the wing – and it caused New Zealand all sorts of problems.

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

'Sudden-death games are won on big moments. They will have their share and have enough experience to take their chances, but I believe the Boks will need a decent lead going into the final quarter. They need to move the All Blacks around, as they do at Ellis Park.'

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