The Waratahs are likely to be without the services of flanker Mitchell Chapman for the remainder of the season.
The 30-year-old suffered a knee injury at training on Monday night and will be sidelined for the foreseeable future.
"He's out for the season, I'd say," coach Michael Cheika told The Australian.
"He might get back for the Reds game, I don't know. He has played well and obviously with the (Wallabies) players who might be missing next week (against the Western Force) he would have been a key ingredient to the team. It's unfortunate, but we are more thinking about this week's game. We'll get onto that one and worry about the rest later."
Pat McCutcheon is the man likely to fill Chapman's boots, with youngster Jed Holloway waiting in the wings.
"McCutcheon will come back into calculations," said Cheika. "That will be a nice addition for us. I've been having a good look at Jed Holloway lately. Had a great game for his club (Southern Districts) on the weekend."