Clarke's men were bundled out for just 151 after he won the toss in a Pool A clash against fellow tournament co-hosts New Zealand at Auckland's Eden Park on Saturday, with left-arm swing bowler Trent Boult taking a career-best five for 27.
"We were extremely poor, there is no doubt about that," said Clarke. "I think credit needs to go to New Zealand bowlers. They bowled really well.
"I think moving forward the balls are going to swing and we've got work to do with the bat. That's for sure."
Australia were well-placed at 80 for one, with opener David Warner (34) and Shane Watson (23) adding 50 for the second wicket before a rapid collapse saw eight wickets lost for just 26 runs.
It was only because of a last-wicket stand of 45 between Brad Haddin (43) and Pat Cummins (seven not out) that Australia avoided their lowest World Cup total of 129, against India at Chelmsford in 1983.
Starc took two wickets in as many balls before last man Boult blocked the final two deliveries of the 23rd over.
The first ball of the next over saw Kane Williamson (45 not out) strike the winning six off paceman Pat Cummins.
Clarke insisted Australia hadn't given up hope of victory after they were dismissed inside 33 overs.
