Australia's returning back row forward David Pocock says the Wallabies are prepared for a fierce and physical South African challenge in Saturday's Tri-Nations opener.

Australia, eager to make up for a humiliating 23-32 loss to Samoa, has included seven regular Wallabies missing from last Sunday's defeat.

Pocock, who has recovered from a foot injury, said Thursday the Wallabies have done a lot at training to turn things around from last weekend.

"Everyone knows when you play South Africa you've got to be up for it," Pocock said. "Otherwise, it's going to be a hard day at the office."

"It's also a big mindset thing; meeting them in that physical battle."

After torrential rain in Sydney, the match is expected to be played in slow and muddy conditions, which scrumhalf Will Genia says Australia will look to take advantage of.

"It's a lot easier, when it's raining, to just turn them around and put it into the corners and try and put pressure on them that way," Genia said.

"You can't throw the ball around as much as you can when it's dry. So we might have to tighten up a little bit as well and we'll just adjust on the night."

Pocock said the wet conditions serve as useful preparation for the World Cup in New Zealand starting from September.

"It'll be good in the long term as far as preparation goes, and good for the side in general to be able to play in whatever conditions and be able to adjust to a different sort of game style."

South Africa has left more than 20 regular internationals at home to rest up ahead of the Springboks' two home Tri-Nations tests and the World Cup starting in September.

"We feel like we can exert pressure on them, not just through our attack but through our defence as well," Genia said.

"Hopefully we can stifle their attack and we're confident that when we have the ball in hand - with the players that we have - that we can score points."

While the Wallabies are bolstered by the return of their big names, 92-test veteran Matt Giteau's World Cup chances are in doubt after failing to make the 22-man squad for Saturday's match - an omission that sparked criticism Thursday.

Genia added that last Sunday's humiliating loss to Samoa has stung the Wallabies and left them ready for anything the unfancied Springboks throw up.

"They can say what they're going to do but they have to execute and we feel like we can exert pressure on them, not just through our attack but through our defence as well," Genia said on Thursday.

"Hopefully, we can stifle their attack and we're confident that when we have the ball in hand - with the players that we have - that we can score points."

SAPA-AP