That's the rapid rise ACT Brumby Christian Lealiifano completed after he was named to replace the injured Matt Giteau in Australia's touring squad for Sunday's Rugby Championship test in Argentina.

Wallabies coach Michael Cheika elected to take no risks on Giteau after he picked up a sternum injury in Saturday's last-gasp win over South Africa.

On Saturday Lealiifano helped Tuggeranong beat Gungahlin in front of a handful of people, trying to remain positive after missing the 31-man squad to play the Springboks.

He was forced to watch the win from home as Canberra teammate Tevita Kuridrani scored a try after the final siren to help the Wallabies start their campaign in style.

But on Monday he flew out with a Wallabies squad to Mendoza minus Giteau, despite scans on the centre's sternum and nose clearing him of serious injury.

While Lealiifano maintained he received no indication of his future with the Wallabies, Lealiifano said conversations with national coach Michael Cheika after his omission for the South Africa test had been encouraging.

"Before I left [Wallabies camp] he said it's a long way off the World Cup squad," Lealiifano said.

"It's still up in the air and everyone is still in contention.

"He was really happy with my form in the back end of Super Rugby. He didn't give me a lot to work on, he's pretty happy.

"He couldn't express enough how hard the decisions were to cut down a pretty good 40 man squad to 31."

Cheika's Wallabies selections have sparked discussion - particularly the decision to start Waratahs No.7 Michael Hooper over Brumbies player David Pocock.

Ben Alexander wasn't named in the original 40-man squad and Waratahs flyhalf Bernard Foley wasn't named in the team to take on South Africa on Saturday night.

But Lealiifano said he respects the job Cheika is doing.

"Give credit to him - he's got the balls to make those decisions," he said.

"You're going to have critics and everyone having their opinion but I've been in camp with the group and the whole time it's been super positive."

"It's just unfortunate that someone has to miss out in a squad that's full of quality players."

Cheika had already indicated he would make some changes to his team for Sunday's match and Matt Toomua looks likely to get a start at inside centre after impressing when he came off the bench against the Springboks.

Australia play New Zealand in the first of two Bledisloe Cup tests in Sydney on Aug. 8, with the second match, which is not part of the Rugby Championship, taking place in Auckland the following week.

Scrumhalf Will Genia (knee) and winger Rob Horne (calf) had already been ruled out of the trip to Argentina and will be replaced in the squad by Nic White and Nick Cummins respectively. with AAP

Revised Wallabie squad: Forwards - James Slipper, Scott Sio, Greg Holmes, Sekope Kepu, Stephen Moore, Tatafu Polota-Nau, James Hanson, Rob Simmons, Will Skelton, James Horwill, Dean Mumm, Scott Fardy, Scott Higginbotham, Ben McCalman, Sean McMahon, Michael Hooper, David Pocock. Backs - Nick Phipps, Nic White, Bernard Foley, Quade Cooper, Matt Toomua, Christian Lealiifano, Kurtley Beale, Tevita Kuridrani, Adam Ashley-Cooper, Drew Mitchell, Joe Tomane, Nick Cummins, Israel Folau. (Reporting by Nick Mulvenney, editing by Greg Stutchbury)