Cape Town - Springbok coach Rassie Erasmus admits that it is a big blow losing Cheslin Kolbe for Sunday's Rugby World Cup semi-final against Wales, but he has expressed full confidence in Sharks speedster S'bu Nkosi.

Kolbe, one of South Africa's standout players at the tournament so far, is out with an ankle injury and Nkosi comes straight into the starting line-up in his place. 

"It is a big blow," Erasmus told media in Yokohama on Thursday shortly after naming his side.

"Everybody knows the quality of player he (Kolbe) is and the contribution he has made. But if we looked purely at his performance in the previous game, his ankle definitely had an influence on his performance.

"We just feel a fully fit S'bu and the way S'bu has been performing, if you compare the two, a 70% Cheslin isn’t better than a 100% S'bu.

"So, it is a blow, but we have full confidence in S'bu, especially with the way he has been playing. He certainly deserves his chance."

Erasmus added that what the Boks might lose in Kolbe's raw pace, they gain in other areas of Nkosi's game. 

"Cheslin’s top-end speed and agility is probably one of the best in world rugby – I think he is up there with Shane Williams and (Damian) McKenzie," said Erasmus.

"That is definitely something we will miss.

"But aerially, S'bu is right up there with what Cheslin and most of the best players in the world can do. And power-wise, S'bu brings something totally different to the party.

"In certain aspects of the game, we will keep it the same. And then other things, a starter move here and there, with the size we have with S'bu, we will maybe use him a little bit differently. On defence, we might use him a little bit differently.

"We will play towards his strength. If you just put the two players next to one another, there are different attributes with each player."

Kick-off on Sunday is at 11:00 (SA time). 

Teams:

South Africa

15 Willie le Roux, 14 S'bu Nkosi, 13 Lukhanyo Am, 12 Damian de Allende, 11 Makazole Mapimpi, 10 Handre Pollard, 9 Faf de Klerk, 8 Duane Vermeulen, 7 Pieter-Steph du Toit, 6 Siya Kolisi (captain), 5 Lood de Jager, 4 Eben Etzebeth, 3 Frans Malherbe, 2 Bongi Mbonambi, 1 Tendai Mtawarira

Substitutes: 16 Malcolm Marx, 17 Steven Kitshoff, 18 Vincent Koch, 19 RG Snyman, 20 Franco Mostert, 21 Francois Louw, 22 Herschel Jantjies, 23 Frans Steyn

Wales

15 Leigh Halfpenny, 14 George North, 13 Jonathan Davies, 12 Hadleigh Parkes, 11 Josh Adams, 10 Dan Biggar, 9 Gareth Davies, 8 Ross Moriarty, 7 Justin Tipuric, 6 Aaron Wainwright, 5 Alun Wyn Jones, 4 Jake Ball, 3 Tomas Francis, 2 Ken Owens, 1 Wyn Jones

Substitutes: 16 Elliot Dee, 17 Rhys Carre, 18 Dillon Lewis, 19 Adam Beard, 20 Aaron Shingler, 21 Tomos Williams, 22 Rhys Patchell, 23 Owen Watkin