In-form Wallabies halfback Will Genia looks certain to miss the season ending clash with England at Twickenham after his French rugby club denied permission to play.
The Wallabies will be trying to finish their spring tour on a high by ending England's unbeaten run under former Australia coach Eddie Jones.
But their hopes of a first grand slam in 32 years were ended by Ireland on Sunday in Dublin.
They will have to win it without the former Queensland Reds star Genia as the match is classed as an out-of-window Test so Stade Francais isn't obliged to release him.
"Right now, from the conversations we've had with Paris, they're not releasing him," said Wallabies coach Michael Cheika.
"We'll have another crack and see what we can do, but it seems unlikely with the French, they obviously place more importance on their game for Will than our international.
"That's the way the rules are, so we'll just have to deal with it.
"We asked last night after the game and that was the response they came back with."
Australia could also be without Dean Mumm after the forward was cited following a dangerous tackle on Ireland's Tadhg Furlong.
Cheika has asked to speak to referees chief Alain Rolland following his the 13-3 penalty count against his side in Dublin but has yet to hear a response to his request.
"I don't want to talk about it (citing) beforehand, I'll talk about it afterwards because whatever you say here you don't want to be held against you when they come up into the hearing," he said.
"You just want to let the procedure pan out and then afterwards we can talk about it.
"It's obviously the citing officer, the off-field referee, who has decided that Dean has committed some offence that the on-field referees didn't see.
"That's what they do. "We'll get our defence right and all going well, he'll get cleared."