Will Genia will lead the Wallabies against New Zealand in Auckland on Saturday, with skipper David Pocock to have keyhole surgery on his knee on Tuesday.
Openside flanker Pocock suffered damage to the articular cartilage in his right knee in the first half of Saturday's 27-19 loss to the All Blacks in the Rugby Championship opener.
Pocock said he wasn't sure how long he was likely to be sidelined.
"He said he wanted to avoid putting a timeline on it till after he (surgeon) actually got in there to have a look,'' Pocock said.
Coach Robbie Deans was philosophical about the injury.
"It's disappointing for him and obviously not what we were seeking, but that's the way it is and it's part of the game,'' Deans said.
Deans said it was likely he would name both other openside flankers, Michael Hooper and Liam Gill, in the 22-man squad for the second Bledisloe Cup Test at Eden Park.
He didn't nominate the starter but said Hooper, who has won three caps, had more background with the team than the uncapped Gill.
Genia has captained Australia once before - against the United States at last year's World Cup.
"He responds to that sort of responsibility and I've got no doubt he will do so here,'' Deans said of Genia.
Halfback Genia said he would lead by deed rather than word.
"I'll just worry about doing my job as a player first and foremost,'' Genia said.
Pocock's injury continued the run of outs in the Wallabies leadership group, with Genia the only one currently fit.
Lock and first-choice captain James Horwill, Pocock and backs James O'Connor and Pat McCabe are all injured.