Half-centuries by Mitchell Marsh and Josh Inglis helped Australia chase down the target with nearly 15 overs to spare, handing Sri Lanka a five-wicket defeat, their third straight loss at the tournament.
"Despite our promising start, we deeply regret not being able to sustain it, resulting in us being limited to a score of 209 runs," Nissanka told reporters on Monday.
"The opposition's bowlers consistently hit good areas during the middle overs, which created a challenging situation for our batsmen.
"I'm hopeful that I can contribute significantly by scoring a substantial number of runs and playing substantial innings in the upcoming matches," Nissanka said.
Sri Lanka next face the Netherlands in Lucknow on Saturday.
Persons:
Pathum Nissanka, Kusal Perera, Mitchell Marsh, Josh Inglis, Nissanka, Aadi Nair, Peter Rutherford
Organizations:
Monday's Cricket, Sri, Thomson
Locations:
Sri Lanka, Lucknow, Australia, Netherlands, Bengaluru