Veteran Australia prop Allan Alaalatoa was ruled out of the third British and Irish Lions test Tuesday, the Wallabies' second injury blow in as many days.
Alaalatoa hurt his shoulder during last week's crushing last-minute 29-26 defeat in the second test at Melbourne, not returning after halftime as the Lions clinched the series 2-0.
His absence explains the call-up on Monday of former All Blacks prop Aidan Ross, who has linked up with the Wallabies for the first time.
It is more likely, however, that Tom Robertson, who came off the bench in the first two tests, or Taniela Tupou will start in the front row on Saturday in Sydney.
"He's a massive part of the group," forward Jeremy Williams said of Alaalatoa.
"We just wish him the best in his recovery and hopefully he'll be back out there soon."
Williams had praise for Ross, who was born in Australia before moving to New Zealand as a child, playing one test for the All Blacks in 2022 before switching allegiances this year.
The 29-year-old was a long-time Chiefs player but he will play for Reds from next season.
"He's a great bloke and he trains really hard," said Williams.
"He's been in a few different systems now so I'm sure he's going to add a lot of value to the group."
Wing Harry Potter has also been ruled out injured, with coach Joe Schmidt having several options to replace him, including Dylan Pietsch, Filipo Daugunu and Corey Toole.
Australia head into the game desperate to avoid a whitewash, after losing the opening test in Brisbane 27-19.
Lock Nick Frost said the team were hungry for another shot at Andy Farrell's men after their disappointment at losing in Melbourne to Hugo Keenan's controversial late try.
"There's a bit of fire in the belly from the last couple of games, and you're playing in Sydney, for a lot of the boys, that's (their) hometown," he said.
"You're playing for your nation, playing for your family first and foremost too."
