South Africa have a new captain for the 50-over format with both Faf du Plessis and AB de Villiers sidelined by finger injuries.
Batsman Aiden Markram has played just two previous ODIs for the Proteas but will captain them in his third with the star players both sidelined.
Markram scored 66 on his ODI debut against Bangladesh last October, and 9 in the opening match of the ongoing six-match ODI series against India, which continues with the second match on Sunday.
The opener has played six Tests for the Proteas, scoring 94 in the Centurion Test against India, but followed that with scores of 1, 2 and 4 to leave the Proteas with some top-order questions ahead of Australia's visit.
South Africa's selectors admitted giving a third-game player the captaincy was a gamble, especially in a series where the world No.1 ranking is on the line, but pointed to Markram's experience guiding the country to the 2014 Under-19 World Cup title.
And while a captain for the T20 series is yet to be decided, and CSA's convenor of selectors, Linda Zondi, said Markram's appointment was with an eye on the future after the 2019 World Cup.
"Part of our plan is to make sure we look at our vision (to) 2019 and also making sure that part of our plan is to develop young leaders in view of the post-2019 plans. I think Aiden fit in," Zondi said.
"We are aware that Markram is new to our set-up. Part of our plan is to also build that pool of leasers within the set-up.
"I think Markram has always been in our plans since he was Under-19 captain, leading up to South Africa A, and now joining the Proteas.
"Yes, there will be pressure in terms of him maybe understanding his role and also being able to perform as a player. For us, we want to see if he can handle pressure. Because part of leadership is to be able to adjust and perform under pressure.
"His awareness of the game, his confidence when making decisions. To lead senior guys, it is always challenging when you are a young guy and you have to make decisions.
"He is the kind of guy, in our opinion, who is willing to open himself to advice. He has got that supporting structure around the team at the moment.
"We have got Hashim, Amla and JP [Duminy]. Guys who are going to be here. Captaincy is a special skill. You don't just wake up one morning and become a captain.
"He has been there, he has done that, it is a matter of us giving him an opportunity."
Markram said he would consult du Plessis and other senior players in the squad, and was humbled by the trust shown in him.
"It's a big honour. Obviously, as a little boy you grow up and you want to captain your country one day," Markram said.
"Unfortunately for the team's sake, Faf misses out. It's a big loss to the side. But then the selectors showing confidence in me to take over, it means quite a bit.
"It's a super humbling experience, but yes, we're going to need to do this for Faf. What happened to Faf in Durban was a freak incident.
"I officially heard (about the captaincy) first thing this morning. I think it's something that you can't take for granted. I really enjoy captaining, but it's an unexpected thing.
"I'll keep sending messages to Faf on and off the field asking for advice. I'll definitely consult senior players for the best interest of the side."
Du Plessis is out of the ODIs and the T20 series to follow and now faces a race against time to be fit for the first Test against Australia on March 1, with a broken digit sidelining the Proteas' first-choice skipper for up to six weeks.
Du Plessis left the field during the first ODI in Durban on Thursday with what he thought was a minor injury to his right index finger.
But Cricket South Africa announced that the finger was broken.
It had previously been announced that former captain AB de Villiers would miss the first three one-day matches, also with a finger injury.
Batsman Farhaan Behardien and wicketkeeper-batsman Heinrich Klaasen have been added to the squad.
Qantas tour of South Africa
Australia squad: Steve Smith (c), David Warner (vc), Cameron Bancroft, Usman Khawaja, Peter Handscomb, Shaun Marsh, Mitchell Marsh, Tim Paine, Mitchell Starc, Josh Hazlewood, Pat Cummins, Nathan Lyon, Jackson Bird, Jon Holland, Jhye Richardson.
Warm-up match v SA Invitational XI, Sahara Park, Benoni, Feb 22-24
First Test Kingsmead, Durban, March 1-5
Second Test St George's Park, Port Elizabeth, March 9-13
Third Test Newlands, Cape Town, March 22-26
Fourth Test Wanderers, Johannesburg, March 30-April 3