The intriguing battle for Wallabies inside-back spots has take another twist after Matt Giteau was ruled out of Saturday's Test against Argentina.

Nose and chest scans cleared Giteau of any serious damage after he copped a battering in his first Test in four years during Saturday's 24-20 comeback win over South Africa.

But coach Michael Cheika ruled the inside centre out of the Test against the Pumas in Mendoza as a precautionary move because of his sternum soreness, with Christian Leali'ifano called into the travelling squad as a replacement.

Cheika said 32-year-old Giteau's leadership would be missed but the 93-cap veteran would be right for the two Bledisloe clashes with the All Blacks that follow the Argentina Test.

"It's going to be a big year for Gits and to send him over to Mendoza after a very physical test as well as a tight turnaround, just isn't fair on him or the group."

Giteau's absence makes it almost certain Matt Toomua will get a starting role after impressing greatly off the bench with a key role in the Wallabies' comeback.

Toomua has played most of his Test rugby at inside centre and could be a straight replacement for Giteau but Cheika could also recall Kurtley Beale.

His options at five-eighth include incumbent Quade Cooper, who had a mixed game, Toomua and Bernard Foley, who occupied the spot for most of last season.

Halfback Nick Phipps appears certain to start after also adding spark off the bench when Will Genia suffered a knee injury which has ruled him out.

Phipps was confident the intensive training camp the Wallabies went through would stand them in good stead.

"I think as Cheik has said, he wants everyone to be able to drop in at a moment's notice, so we're pretty lucky we've been training that way," he said.

"It will be interesting to see who the 10-12 is leading down the track and then we can just build from there straight away.

"There's always a lot of onus put on partnerships, but everyone has been rotating with each other from the Brumbies halves, the Reds halves and the Waratahs halves. Even having Matty [Giteau] at 10 in the back half of the game on the weekend felt comfortable.

"I think the coaches are quite spoilt for choice."

Phipps started against the Pumas in Mendoza last year but got a yellow card early in the second half of a 21-17 loss.

"They [Argentina] are phenomenal, they always punch above their weight," Phipps said. "Every year they keep improving." - AAP