Australia captain Michael Clarke admitted there was "no excuse" for his side being bowled out for just 74 in the third one-dayer against Sri Lanka.
The hosts at one stage found themselves 40-9 in Brisbane and only avoided recording their lowest ever total in 50-over cricket thanks to a last-wicket stand between Mitchell Starc (22 not out) and Xavier Doherty (15).
Clarke, who contributed nine runs, the highest score by anyone in the top eight of the order, pulled no punches with his assessment of an Australian innings that lasted 26.4 overs.
"Our defence let us down more than anything. No excuse for the way we performed," he said.
"Shot selection was poor. I understand the public wants us playing consistently. Honestly, if we played like that then the public wouldn't want to see us playing at all."
Nuwan Kulasekara did the early damage for Sri Lanka, claiming 5-22 from his 10 overs. There was also three wickets for Lasith Malinga in an innings that lasted 26.4 overs.
"Nuwan has been very consistent for us for quite a few years and he's built a nice little partnership with Lasith (Malinga)," Sri Lanka skipper Mahela Jayawardene said.
"The thing today was he hit some really awkward areas for the Aussie batsmen and especially on this wicket created a lot of problems."
The tourists did have a few issues with the bat themselves, losing six wickets before reaching their target of 75 with an astonishing 30 overs to spare.
The series now moves onto Sydney for the fourth game on Sunday, before concluding in Hobart on January 23. The two nations then play two Twenty20 Internationals.