Timana Tahu's big-game experience will help him succeed in one of rugby's toughest arenas when he makes his run-on debut for the Wallabies in Johannesburg, says coach Robbie Deans.

Tahu was named to start against South Africa at hoodoo ground Ellis Park on Saturday after playing just 23 minutes of Test rugby off the bench in his previous two appearances.

Deans is an avowed fan of the former NRL premiership winner, State of Origin star and Kangaroo and said those experiences would help Tahu in front of the fanatical Jo'burg rugby fans.

"You don't achieve or have the sort of longevity that he's had in any code, in any sport, without loving the challenge and without wanting to be tested and being prepared to put yourself outside your comfort zone to do that," Deans said.

"He appears composed and hopefully he is because he's got an awful lot to offer and we just want him to bring what he does have to offer and play with confidence."

Tahu, who replaces the injured Berrick Barnes, was one of five changes to Australia's run-on side following last week's drought-breaking 27-15 win over the Springboks in Durban.

Adam Ashley-Cooper returns at fullback after overcoming a hand injury, Phil Waugh starts at openside flanker, Hugh McMeniman replaces injured lock Dan Vickerman and Tatafu Polota-Nau has been named at hooker.

The Wallabies received a boost when tough blindside flanker Rocky Elsom was successful in appealing a one-match ban for dangerous play in a lineout.

"There's been two unforced changes (Waugh and Polota-Nau)," Deans said.

"We're just reversing the roles I guess, those blokes are doing some yards for the others for a change.

"The other changes were essentially forced ones.

"Hugh's obviously returning from illness and then we've got the two injuries to Dan Vickerman and Berrick Barnes so Timana Tahu gets a start which is great for him."

Deans is wary of the wounded Springboks, who have been under the pump all week following successive home losses.

"They have got one more shot at it in this year's Tri-Nations," he said.

"If they can take it, they can park the rest of the tournament and move forward a lot more positively towards their end of season tour preparations.

"Ask yourself how you'd feel in their position. There's no doubt they'll be up for it.

World Cup holders South Africa are out of the running to win this year's Tri-Nations title, which will be decided when Australia host the All Blacks in Brisbane next month.

"Saturday still has huge significance - both in terms of momentum in the Tri-Nations, but also as far as the development of our group as a whole is concerned," Deans said.

Australia have only once previously won consecutive Tests in South Africa, 45 years ago.

That 1963 success remains Australia's only win from nine attempts in Johannesburg.

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