Winger Tune joined the Wallaby squad in Durban on Tuesday night after the Australian Rugby Union decided not to punish him for taking the banned substance probenecid.

An ARU tribunal accepted Tune's explanation that he had taken the drug to speed up his recovery from a knee injury.

But the ARU did not report the matter to the International Rugby Board when Tune tested positive and the world governing body could still overturn the decision.

"It's done with as far as I'm concerned, and I'm looking forward to playing on Saturday," said Tune.

"I'm not sure what else the IRB want me to do. I've followed the process and an independent committee has found me guilty but didn't think I deserved a penalty.

"So that's that. What the IRB do from now on is up to them, and I'm trying not to worry about it.

"We have a very strict doping policy and I think Australia is, in general, probably one of the most drug-free countries in world sport."

Australia make just one change to the side which beat New Zealand 16-14 in Sydney on 3 August, with tighthead prop Ben Darwin coming in for Patricio Noriega (ear infection).

Rod Moore replaces Darwin on the bench.

Wallaby captain George Gregan will make his 78th international appearance - a world record for a scrum-half - and flanker Owen Finegan will win his 50th Test cap.

South Africa, meanwhile, are confident they will avoid a Tri-Nations whitewash and prevent Australia from taking the title.

The Springboks have lost all three of their matches in this year's tournament, and will suffer their first clean sweep of defeats in the championship if they lose on Saturday.

They come up against a Wallaby side needing to secure victory by at least 25 points to top New Zealand in the final standings.

"We're confident that if we play the way we have been playing, and a couple of refereeing calls go our way, we'll be in good shape," said Springbok assistant coach Tim Lane.

Head coach Rudolf Straeuli has named an unchanged 22-man squad but could make changes when the final 15 is decided on Thursday.

South Africa squad:
Werner Greeff, Brent Russell, Dean Hall, Adi Jacobs, Marius Joubert, De Wet Barry, Breyton Paulse, Andre Pretorius, Johannes Conradie, Neil de Kock, Bob Skinstad, Joe van Niekerk, Corne Krige, Hendro Scholtz, Victor Matfield, Jannes Labuschagne, AJ Venter, Willie Meyer, Faan Rautenbach, James Dalton, Ollie le Roux, Lawrence Sephaka.

Australia team:
Chris Latham; Ben Tune, Matthew Burke, Daniel Herbert, Stirling Mortlock; Stephen Larkham, George Gregan (capt); Toutai Kefu, George Smith, Owen Finegan, Justin Harrison, Nathan Sharpe, Ben Darwin, Jeremy Paul, Bill Young.