The Australian Rugby Union says it's up to SANZAR to investigate whether South Africa's mass player withdrawals for their upcoming Tri-Nations encounters in Australia and New Zealand are legitimate.

The Springboks are set to field a second-string side against the Wallabies in Sydney on July 23 after team manager Andy Marinos said 21 of their preliminary World Cup squad were injured and unavailable for their opening two away Tri-Nations matches.

It leaves just fly-half Morne Steyn, hooker and captain John Smit and No.8 Pierre Spies as probable first-choice players in contention when the squad is named on Saturday for the Tests in Sydney and Wellington.

Fullback Francois Steyn, wingers JP Pietersen and Bryan Habana, centres Jaque Fourie and Jean de Villiers and scrum-half Fourie du Preez are among eight backs on the casualty list.

The 13 forwards ruled out include props Tendai Mtawarira and Jannie du Plessis, locks Bakkies Botha and Victor Matfield and flanks Schalk Burger and Juan Smith.

ARU chief executive John O'Neill was left fuming in 2007 when the Springboks, in a bid to keep their best players fresh ahead of the World Cup, selected a second-string squad for their Tri-Nations clash in Australia.

At the time, O'Neill labelled South Africa's ploy as "simply not in the spirit of the game".

But although the ARU aren't treating the Springboks' latest move as sinister just yet, they hope SANZAR will investigate the circumstances further.

"The SANZAR joint venture is quite specific about the three countries making best endeavours to field their best available teams and we also have that assurance in writing from the SARU chief executive," an ARU spokesperson said.

"We can't comment from here on what their injury status is, but I'm sure the SANZAR administration will take that up with SARU."

South African team doctor Craig Roberts said that while a number of players faced a race against time to be fit for the two-fixture home leg of the Tri-Nations in August, no one had been ruled out of the World Cup.

"Schalk Burger and Duane Vermeulen recently sustained serious injuries and will definitely not be ready to take part in the Tri-Nations," Roberts told a media conference.

"But we are hopeful that others who have had long-term injuries, such as Juan Smith, Heinrich Brussow and Gurthro Steenkamp, may be available at some point in the series."

Defending champions South Africa will name a 30-man World Cup squad on August 23, fly to New Zealand on September 1 and begin their defence of the William Webb Ellis trophy 10 days later in Wellington against Wales.

The Wallabies will announce their initial 40-man squad on Sunday for the upcoming Test season.

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