The Wallabies are confident Berrick Barnes will be fit to tackle the Springboks in Saturday's Tri Nations Test despite being injured in a collision with prop Al Baxter during Friday's captain's run at Newlands.

Barnes required treatment for a dead arm but the Wallabies' medical staff say he is certain to play.

The Wallabies, already big underdogs to score their first win in Cape Town since 1992, could ill-afford to lose their classy inside centre, whose tactical kicking game will be vital to Australia's chances of springing an upset.

Lock James Horwill was rested from the captain's run as he recovers from a virus which sidelined him from training for two days running.

The Wallabies also insist he is in no doubt of missing the match.

Among the many challenges facing Robbie Deans' side is trying to counter in-form flanker Heinrich Brussow, who has been a key figure in South Africa's recent series win over the British and Irish Lions and the Boks' twin defeats of the All Blacks.

"He's obviously a very good player," Deans said.

"Rugby's a game about instinct as much as anything and instinctively he's very good.

"He puts himself in good position; he's capable of doing that in the first instance, but he picks his moments pretty well.

"There's no doubt he's added a dimension to this (Springboks) side.

"They're already a pretty formidable outfit and he's added an element around the contact.

"They were always very aggressive. He adds a little bit of subtlety as well."

Wallabies fullback Adam Ashley-Cooper is also steeling himself for a tough day at the office.

"Approaching any Test match, you look at the (opposition's) 9-10 combination. South Africa have got du (Fourie) Preez and (Morne) Steyn there and they're great kickers of the ball," said Ashley-Cooper.

"Du Preez off the base with his box kicks and Morne all around the park kicks particularly well and tactically well.

"So I'll be tested there, every fullback is, and hopefully I'll execute on the day and just contribute as much as I can from the back."

Springboks lock Victor Matfield says the world champions are expecting the Wallabies to prove a more challenging prospect than the erratic All Blacks.

"I don't think the Aussies will make the same mistakes," Matfield said.

"They've got a great goalkicker in Matt Giteau but also, when they get into the right areas of the field, they like to build phases and they're really good at that as well.

"So we'll have to be ready for everything."

The Test kicks off at 1am Sunday (AEST).

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