Australia hooker Stephen Moore will not play in Saturday's must-win Rugby Championship clash against South Africa due to an injured hamstring.
Moore, who was poised to become the Wallabies' most capped hooker this weekend in Perth, had scans on Thursday after tweaking his hamstring in a training mishap and has subsequently been withdrawn from the team.
Australia coach Robbie Deans has upgraded NSW Waratahs hooker Tatafu Polota-Nau from his spot on the bench and brought Saia Fainga'a of the Queensland Reds into the squad.
Before Moore was ruled out, Australian prop Ben Alexander claimed the loss of the Wallabies' regular hooker would not affect preparations to face the Springboks. He said: "We've been practising with lots of different combinations. We very rarely pack a couple in a row with the same guys, always changing props, changing sides, changing hookers.
"It shouldn't cause any problems. If (Polota-Nau) gets a chance we know what he's capable of."
The Wallabies enter Saturday's game looking for their first victory of the Rugby Championship after opening with consecutive losses against New Zealand. Deans has come under heavy scrutiny for his side's performances but Alexander said they were working hard to respond this weekend.
"We feel a responsibility for the side not performing," he said. "We're all very proud Australians. The country deserves a better performance than they have had to put up with in the past few weeks.
"In that criticism of Robbie, it obviously hurts us too because it's how we play it. It's a reflection of us and how we represented our country and we didn't do a great job."
The Springboks opened their account with a win and an unimpressive draw against competition newcomers Argentina. Alexander said the new-look South African team would provide a sense of the unknown.
"When they had such a consistent side for so long you knew they'd bring and with guys like John Smit and Victor [Matfield] you mentally knew what you were up for and what you had to do to try stop them," he said. "With this younger side and a new coach they'll do some things differently."