Sri Lanka opener Dimuth Karunaratne was rushed to hospital after a frightening blow to his head on the second day of second Test in Canberra the visitors chased a massive Australian first innings total.
Australia resumed day two on 384 for four and extended their lead to a massive 534 for five when Tim Paine declared.
At stumps, Sri Lanka were 123 for three in reply.
Sri Lanka's openers weathered the new-ball attack led by under-pressure Mitchell Starc with relative ease. Karunaratne and Lahiru Thirimanne saw off some the pace barrage and built an 82-run stand before disaster struck.
Playing in his 58th Test, Karunaratne was 46* when a rising Pat Cummins ball glanced off his shoulder and onto his helmet, close to the neck area.
He slumped to the ground, dropping his bat as Australian players ran to assist.
A doctor and physio sprinted onto the ground and called for more medics and after some 10 minutes, he was put on a stretcher and taken off the field on a golf buggy.
Cricket Australia said he complained of pain in the neck and tingling to the hands and was rushed to hospital.
Coach Chandika Hathurusingha said later he was in "good spirits" and "in no danger".
It clearly unsettled Thirimanne who fell to spinner Nathan Lyon for 41 in the next over, caught by Usman Khawaja at slip.
Cummins then clean-bowled Kusal Mendis for six and when captain Dinesh Chandimal gloved a Starc ball to Paine behind the stumps for 15, the tourists were in trouble.
"We lost a couple of wickets afterwards so it was definitely a distraction." admitted Hathurusingha.
The impressive Kurtis Patterson was unbeaten on 114 and Paine on 45 at the declaration with Vishwa Fernando the pick of the Sri Lankan bowlers with 3-126.
After being dropped on his first ball, Patterson never looked back. The New South Welshman shored up his credentials ahead of an Ashes tour to England later this year by bringing up his maiden hundred with a drive to mid-off for three after starting the day on 25.
Following a century drought stretching back to October when Khawaja scored 141 against Pakistan in Dubai, it turned into a flood in Canberra with three players bringing up the magical mark.
Joe Burns punished the inexperienced Sri Lankan attack on Friday in a 308-run stand with Travis Head (161), carrying his bat through the day.
But he only lasted five overs Saturday after resuming on 172, adding eight runs before chopping a delivery from quick Kasun Rajitha onto his stumps.
Burns' departure brought the consistent Paine to the crease, who kept the pressure on the visitors, still reeling after being beaten at the first Test in Brisbane by an innings and 40 runs.