Australian paceman Josh Hazlewood has been sent off for scans on his left hamstring after limping out of the first Test against New Zealand on Friday.
Hazlewood was running in for the third ball of his second over when he abandoned the delivery and then later trudged off.
The 28-year-old felt for his left hamstring the delivery before, and he was downcast as he limped off the ground with his cap hiding his face.
Australia confirmed Hazlewood had suffered a suspected strain.
Just minutes earlier he produced a brilliant in-swinger to bowl opener Jeet Raval for one, reducing NZ to 2-1 in reply to Australia's 416.
Australia don't have an allrounder in their current XI.
It means if Hazlewood is unable to bowl for the rest of the match, it would heap extra pressure on fellow pacemen Mitchell Starc and Pat Cummins.
Both Starc and Cummins have battled injuries in the past, and Australia would be reluctant to overwork them in the Perth heat, with a top of 41 degrees celsius forecast for Saturday.
Spinner Nathan Lyon and part-timer Marnus Labuschagne could bowl extra overs to cover the absence of Hazlewood.
And Matthew Wade will also come into play, with the former wicketkeeper thrown the ball in the eighth over of the innings to unleash some of his medium pacers.
Wade produced a pearler of a delivery first up, but the majority of his opening over was wayward.
Michael Neser and James Pattinson are part of the wider squad, and one of the duo will come into the selection frame for the Boxing Day Test if Hazlewood is unable to recover in time.
New Zealand are also down a bowler for the first Test after debutant paceman Lockie Ferguson injured his right calf on the opening day.
Australian Associated Press