Wallaby coach Robbie Deans has instructed his charges to use brains, not brawn, to beat the Springboks when the two teams go head-to-head in their crucial Tri-Nations encounter at the Subiaco Oval in Perth on Saturday.

It is Australia's opening match of the series, after South Africa went one-and-one against New Zealand — the Boks losing 8-19 in the opening round in Wellington and recording a historic 30-28 win in Dunedin last week.

Deans, despite his Australian outfit disposing of both Ireland and France last month, is aware that the Boks is a big step up from their June internationals.

And having had the opportunity to study the Springboks in back-to-back encounters with the Kiwis, Deans knows that creativity will be the key to upstaging the World Cup champions.

The Wallaby mentor, Deans, made it clear that his team will need to be "inventive" to start their Tri-Nations campaign on a winning note.

"I hope that's the outcome," Deans said when asked about his team's brains beating the Bok brawn.

"We have to play. We won't be able to be conservative against a side that has the physical capabilities of the South Africans, and get home. The key will be to keep them busy, with the traffic going the other way."

Deans urged his players not to shy away from their expansive game plan, even when the heat is on in Perth.

The Wallabies will also be playing their first game under the revised Experimental Law Variations (ELVs) that will be in force for the Tri-Nations, while South Africa have already shown they have the skills and muscle to cope with the new laws.

The Boks have managed to combine their traditional forward power with a dash of brilliance, but Deans knows that it is the Bok power plays that could hurt his team most.

"Believe me, the physicality is still there," Deans said.

"You only had to look at the two tests between the All Blacks and the Springboks to recognise the physicality didn't diminish at all, but they were a little bit more prepared to use the width of the ground and, to be frank, that makes them harder because you can't presume.

"It makes them a more challenging opponent to defend against.

"We are going to have to play."

365