Sydney - Cancer survivor Christian Lealiifano was recalled to the Wallabies for the first time in three years on Thursday, but there was no room for Quade Cooper or Nick Phipps in their squad to face South Africa.
Brumbies skipper Lealiifano hasn't featured for Australia since 2016, just months before he was diagnosed with leukaemia.
But he has been in top Super Rugby form to earn his place alongside fellow flyhalves Bernard Foley and Matt Toomua in the 34-man squad for their Rugby Championship opener in Johannesburg on July 20.
His inclusion means there was no room for mercurial playmaker Cooper, who has been capped 70 times but has not been picked since mid-2017 after falling out of favour.
Cooper had resurrected his career with a move to the Melbourne Rebels this year and was in impressive early-season form, combining well with Wallabies scrumhalf Will Genia.
It prompted national coach Michael Cheika to say in March he was in "strong contention" for a recall, but his omission leaves his World Cup chances hanging by a thread.
"I'm not the expert to speak on what Christian has been through, only he knows that and his family," said Cheika, referring to Lealiifano's cancer battle.
"What you can't deny is his form in Super Rugby at the end of the day. If you take out all the other things that he's achieved, he's been playing good in Super Rugby and deserves to be there."
The Brumbies made the Super Rugby semi-finals, and their front row of James Slipper, Scott Sio, Folau Fainga'a and Allan Alaalatoa were rewarded by being selected.
Other big names to miss out were Tatafu Polota-Nau, Ned Hanigan and former bad boy James O'Connor, although forward Tolu Latu, who was charged with drink-driving in May, was picked.
O'Connor was the second-youngest Wallaby ever when he made his debut at 18 in 2008, but a string of off-field incidents brought his international career to a crashing halt on 44 Test caps.
Earlier this week, he left Sale Sharks to make a last-gasp attempt for inclusion in the World Cup squad but is still reportedly in the process of finalising a Rugby Australia contract, which would allow him to play for the Wallabies.
The experienced Phipps was also overlooked with Nic White getting the nod for the first time since 2015 after his return from playing in England. He joins Genia and Joe Powell as the scrumhalves.
Three potential debutants were included - No 8 Isi Naisarani and backrowers Liam Wright and Rob Valetini with David Pocock, Adam Coleman and Pete Samu missing through injury.
Cheika said the selection process was "really tough", with a new panel now in place, including new director of rugby Scott Johnson, after a shake-up following just four wins from Australia's 13 Tests last year.
"It was the first time we've worked as a selection panel with different voices and different opinions challenging each other but I think we've come to a better outcome than if I was just picking it myself," he said.
The Wallabies travel to Johannesburg on Sunday for a week-long training camp on the highveld to prepare for the high altitude conditions.
Allan Alaalatoa, Rory Arnold, Jack Dempsey, Folau Fainga'a, Michael Hooper (captain), Luke Jones, Sekope Kepu, Tolu Latu, Isi Naisarani, Tom Robertson, Izack Rodda, Rob Simmons, Lukhan Salakaia-Loto, Scott Sio, James Slipper, Taniela Tupou, Jordan Uelese, Rob Valetini, Liam Wright
Adam Ashley-Cooper, Tom Banks, Kurtley Beale, Bernard Foley, Will Genia, Dane Haylett-Petty, Reece Hodge, Samu Kerevi, Marika Koroibete, Tevita Kuridrani, Christian Lealiifano, Jack Maddocks, Joe Powell, Matt Toomua, Nic White