The Waratahs are sweating over the fitness of openside flanker Michael Hooper who limped off during his side's 18-11 defeat to the Western Force on Saturday.
Hooper appeared to sustain a knee injury in the 69th minute of the clash in Perth after taking a hit off the ball from Force lock Wilhelm Steenkamp.
The Wallaby captain tried to play on but was eventually forced to leave the field for the first time in more than a year.
Waratahs boss Michael Cheika admitted that Hooper's injury was a big concern.
"He got a bump on his knee, but it happens when you get tackled without the ball," he told the Sydney Morning Herald.
"[When] you're not expecting to get hit and you get hit, you get injuries.
"I don't know how bad it is but it doesn't look great."