Rising star Cameron Green took a fierce blow to the head while bowling on Friday as depleted Australia suffered a fresh concussion scare against India A ahead of next week's first Test.
Green was bowling to Jasprit Bumrah when the tail-ender smacked the ball straight back, striking him in the side of the head with a sickening crack.
Indian batsman Mohammed Siraj immediately threw his bat aside and ran to Green's aid as the bowler dropped to the floor.
Green, whose century against India A this week put him in contention for a first Test cap, eventually walked off the ground unaided. There was no immediate word on the extent of his injury.
The incident comes just three days after fellow Test hopeful Will Pucovski suffered "mild concussion symptoms" after being hit on the head while batting against India A.
Pucovski is seen as a potential replacement for opener David Warner who has been sidelined by an adductor injury, up-ending the Australian top order.
Twenty-year-old Green was recently described by Greg Chappell as the best he had seen since former Test captain Ricky Ponting.
The all-rounder has been in sizzling form with the bat and his unbeaten 114 against a quality India A attack featuring Ravi Ashwin and Kuldeep Yadav left selectors with plenty to ponder.
Australia open their four-Test series against India with a day-night game in Adelaide from December 17.
In Friday's game, India A were rolled for just 194 by Australia A, in the tourists' only pink ball warm-up for the opening Test.
With Virat Kohli opting not to play, the team struggled at an overcast Sydney Cricket Ground against a second-string attack missing frontline bowlers like Josh Hazlewood and Pat Cummins.
While Australia are a seasoned day-night side, having played seven and won the lot, India have experienced just one pink ball Test -- in Kolkata last year, when they thrashed Bangladesh.