Leg-spinner Adam Zampa roared back to form with a four-wicket haul as Australia bowled out Sri Lanka for 209 in the World Cup here on Monday.
An out-of-form Kusal Perera (78) got some much-needed runs while Pathum Nissanka struck 61 for his second consecutive fifty.
Australia benefitted from the timely return to form of Zampa, who had been having an awful tournament. The wrist spinner enjoyed an excellent outing to help bundle out Sri Lanka in 43.3 overs.
Looking on course for a 300-plus score, the 1996 winners faced a bizarre batting collapse and went from 125 for no loss to 209 all out.
There were lots going on in the field as Mitchell Starc aborted his delivery stride thrice to warn Perera to not leave his crease early on at the non-striker's end.
Perera was also struck in the head by a Marcus Stoinis bouncer which caught the Sri Lankan off guard.
But the experienced southpaw didn't let the blow deter him and went on to send Stonis' slower cutter down the ground to bring up his fifty.
With both openers pilling on the runs, the Australian bowlers looked clueless. But skipper Pat Cummins kept shuffling his bowlers in search of that first breakthrough.
Cummins, who has been far from his best with the ball, stood up at the opportune moment to give Australia the breakthrough they needed.
Cummins cramped Nissanka for room and the Sri Lankan hit it high and in front of square only for David Warner to run and complete a stunning catch.
Cummins bowled a peach of a delivery five overs later to clean up the other set batter in Perera, who picked the wrong line to swing his bat.
The dismissal marked the beginning of Australia's dominance as the Sri Lanka batting unravelled and the five-time champions grew in confidence.
Zampa got rid of the in-form Kusal Mendis. But the wicket belonged to Warner who ran across from deep midwicket, covering about 25ms to complete a spectacular diving catch.
Sadeera Samarawickrama, Chamika Karunaratne and Maheesh Theekshana were Zampa's other victims with Mitchell Starc pitching in with two wickets.
Apart from the openers and Charith Asalanka's 25, no other Sri Lankan batter reached double digits.