The Wallabies have been left with no specialist five-eighth to call on, with Carter Gordon expected to be ruled out of the World Cup with a knee injury and lock Nick Frost set to join him.
While the Australians don't know if they will have another World Cup match, with their quarter-final hopes hanging on Fiji's next result, coach Eddie Jones said the pair were unlikely to take any further part in the France tournament.
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But Jones said that if the Wallabies do survive to face Pool D winners England in the play-offs in Marseille on Sunday October 15 (October 16 AEDT), skipper and lock Will Skelton and spearhead prop Taniela Tupou should be available.
Youngster Frost, who has been one of Australia's best, was replaced a minute into the second half of the Wallabies' 34-14 win over Portugal after injuring his knee late in the opening period.
Gordon was injured at training and ruled out just before the Saint-Etienne match.
"It's unlikely that Nick and Carter will take any more part in the tournament," Jones said.
"Conversely, we've got Taniela and Will, and if we have another game they will be ready to go."
Jones said he didn't think Gordon would require surgery while Frost would go for scans.
"(The knee injury) happened when he was warming up on Thursday, but it was only an irritation and since then we had a scan and it looked more serious than we thought," he said of Gordon.
Jones gambled with selecting just one specialist five-eighth in the squad in Gordon, overlooking veterans Quade Cooper and Bernard Foley.
However he replaced the Rebels No.10 in the starting role with utility Ben Donaldson following a poor showing in the team's loss to Fiji.
He could call in injury cover for Gordon, while the Wallabies still haven't replaced young fullback Max Jorgensen, who fractured his leg at training last week.
"We have players training in different positions and particularly since the advent of HIA (head injury assessments) you've got to become a lot more flexible," Jones said.
"We'll just make a judgment later in the week about what we do there."
