The Wallabies were unable to disguise their anguish after botching a golden opportunity to burst the Springboks' bubble in Cape Town on Saturday.

As he twice did against the All Blacks, superboot Morne Steyn punished the Wallabies for an ill-disciplined, mistake-riddled performance to pile on 24 points as the high-flying Boks continued their unbeaten start to the Tri Nations with a clinical 29-17 victory at Newlands.

Compounding Australia's pain was a knee injury to skipper Stirling Mortlock which could rule the Wallabies captain out for the rest of the tournament.

After being replaced in the 20th minute, Mortlock was taken to hospital on crutches amid fears he may have broken his leg.

But x-rays revealed no fractures and Mortlock was to have further scans upon returning to Australia on Monday, with the Wallabies doctor suspecting the veteran centre had torn the meniscus cartilage in his right knee.

At best, Mortlock is in serious doubt of being fit to tackle the All Blacks in Sydney on Saturday week, August 22.

At worst, he could miss all four of the Wallabies' remaining matches in the annual southern hemisphere championship.

The captain's sorry state capped a rueful day for the Wallabies, whose alarming lack of composure once again cost Robbie Deans's rebuilding side any realistic chance of upsetting the rampant world champions.

Coach Deans was infuriated by one diabolical five-minute stretch early on that allowed the Springboks to turn a 7-0 deficit into a two-point advantage.

"It gives them a leg up and an unnecessary leg-up," Deans said.

The Boks maintained the momentum to surge to a match-winning 23-10 lead at the break.

The joy of Adam Ashley-Cooper's try after just 98 seconds was long forgotten when the Wallabies were reduced to 13 men for 10 minutes either side of halftime when Matt Giteau and flanker Richard Brown were both in the sin bin.

George Smith completed Australia's miserable afternoon when he was the third Wallaby yellow-carded in the dying minutes.

"We're just killing ourselves," Wallabies centre Berrick Barnes lamented.

"We were tough and that's the whole Australian thing, but we've got to be better for 80 minutes and not just at times when we are really under the pump.

"That's the key to it. It's the area that we've got to improve and it's been the case with us for a little while now."

Hooker Stephen Moore summed up the frustration in the Wallabies dressing room.

"Our poor discipline let them into the game too much in that first half," Moore said.

"We seem to be always giving away penalties on that 40-metre mark and you saw how Steyn puts them away.

"We talked about being in those positions during the game and probably didn't react the way we should have.

"We lost our judgement."

Most disturbing for Deans were the nine lineouts lost on the Australian throw, with South Africa's champion locks Bakkies Botha and man-of-the-match Victor Matfield destroying the Wallabies.

"When you're against the best side in the world, you can't afford not to get what's there for the taking," Deans said.

"Your throw - when you turn that over, they turn the tables on you. It didn't allow us to change the terms of engagement and we lost field position quite routinely.

"But we showed when we had possession what we're capable of. We created a lot of stress; we actually converted it with two tries to one and we won the second half.

"Last year we probably would have capitulated ... under the circumstances, against the best side in the world, down to 13 men, I don't think there would have been too many that would have won the second half.

"So that's a point of difference."

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