Springbok coach Peter de Villiers, already faced with the fact that he will be forced into at least two changes, has two more players on the doubtful list ahead of their Tri-Nations showdown with the Wallabies in Brisbane on Saturday.

Already wing JP Pietersen (hamstring) and replacement lock Andries Bekker (shoulder) have returned home after being injured in last Saturday's 32-25 win over Australia in Perth.

Pack enforcer Bakkies Botha is now also in doubt with abdomen and knee problems, while possible replacement, Danie Rossouw, is working his way back from a hamstring strain.

Botha and superstar wing Bryan Habana (groin) both sat out training on Monday.

However, Habana has been ruled fit to play as the world champions search for their first win in Brisbane since 1971.

"The Bakkies injury is more of a worry than anything else, especially since Danie is fit but hasn't played for a while," said De Villiers. "We haven't used him a lot and we'll have to see whether he can be an 80-minute player.

"Bryan is more precautionary, he was rucked in the groin, but he could have trained today [Monday] if he had to. But it's a tough tour and the management of the players is important."

De Villiers, who said he was reluctant to call for replacements out of South Africa, will give Botha as much time as possible to prove his fitness.

"I don't want to weaken the provincial sides and then not use someone I've called over. But I will speak to the doctor and see if we really need someone."

South Africa needs just two more bonus points from their remaining two games to clinch the Tri-Nations title.

The Boks play the Wallabies in Brisbane on Saturday and then face New Zealand in Hamilton a week later.