The Wallabies have rushed rookie hooker Billy Pollard to Argentina ahead of their Rugby Championship opener after Dave Porecki suffered a concussion in training.
Porecki will be unavailable for the first Test against the Pumas in Mendoza on Sunday (AEST) but could play in their second match in San Juan a week later.
It's a blow for the Australians with Waratahs rake Porecki a breakout star during their series loss to England last month, starting in all three Tests.
It follows shattering news that Wallabies star Samu Kerevi will require a knee reconstruction after sustaining an injury while on Commonwealth Games duty with the Sevens team.
Brumbies hooker Pollard, 20, caught the eye of Wallabies coach Dave Rennie despite playing only eight Super Rugby matches since making his debut in 2021.
He won selection in the Australia A program and was preferred over Feleti Kaitu'u and Matt Faessler to start against Samoa and Tonga.
The absence of Porecki means Folau Fainga'a is likely to wear the No.2 jersey with Lachlan Lonergan coming onto the bench.
Rennie is set to announce his team to face Michael Cheika's men overnight Thursday.
