The Wallabies should not underestimate the hunger of a second-string Springbok team in this weekend's Tri-Nations' opener, South Africa back Adrian Jacobs said on Monday.

The world champions have 23 players missing from their Australasian tour through injury - including vice-captain Victor Matfield, hooker Bismarck du Plessis, lock Bakkies Botha and wing Bryan Habana.

In their absence coach Peter de Villiers has named a largely untried squad for South Africa's two away Tests against the Wallabies (in Sydney on Saturday, July 23) and New Zealand (in Wellington a week later).

Despite the absence of the Springbok stars, Jacobs insists the lure of making the squad for this year's World Cup is a huge incentive for the players.

"We've got guys in the squad who have played Tests before and all of us are looking forward to playing," Jacobs told reporters on Monday.

"We want to show the world we didn't come over here to fool around. We're here to play.

"There are a lot of places in the side still open and the guys at home will know that many of this team can go to the World Cup and this is an opportunity for every player to show that they are good enough to wear the jersey."

The Sharks centre, 30, said he is desperate to play in the World Cup, which starts in New Zealand in September, and believes a strong start to the Tri-Nations campaign against the Wallabies will hold him in good stead.

"I have played 30 Tests, but I have never gone to a World Cup and it is something to work on, and it's my dream to be involved in one," he said.

"I need to show that I can still make it. We have a lot of critics at home that don't think we can and it's up to us to prove that we are."

The Wallabies will be looking for retribution against the Springboks after their shock 32-23 defeat to Samoa but Jacobs believes little should be read into Sunday's result.

"It was a bit of a surprise for all of us, but Australia is a proud nation and, like all good teams, they will bounce back, hopefully not this week," he said.

* Meanwhile World Cup-winning lock Johann Muller and star flank Heinrich Brüssow trained on their own on Monday as the Springboks had their first field session in Australia in preparation for Saturday's Tri-Nations Test against the Wallabies in Sydney.

The pair continued their rehabilitation from hamstring and knee injuries respectively as the team practiced on a dry and sunny morning at the North Sydney Oval.

All the other 26 players took a full part in the session, which Springbok coach Peter de Villiers said was designed to loosen up the players after the delayed flight to Sydney on Saturday.

"The boys had a good run out to shake the trip out of their systems and we're back in the full swing now," said De Villiers.

"Johann and Heinrich are coming along nicely and we'll give them another 24 hours before making a final decision."

The Springboks name their team for the opening Tri-Nations test of the season on Tuesday.