Two-try full-back Chris Latham says there is much more to come from Australia after the 32-20 win over Wales at Cardiff's Millennium Stadium.
Latham's second try ended hopes of a Wales comeback
"We're still warming up in this tournament," said the man-of-the-match.
"That was a great, spirited performance to get a victory in Cardiff. We were a bit loose at times, but we stuck at it, even when we were down to 13 men.
"I was happy with two tries, but credit goes to the forwards. They built the platform and were superb in defence."
The victory gave Australia control of Pool B and means they are likely to face either England or Samoa in the quarter-finals in Marseille.
Wallabies coach John Connolly had some words of comfort for Wales as he spoke about their chances in the tournament.
"They've got some very good players," he said. "I wouldn't be too hard on them. They'll get past Fiji and Japan.
It was an outstanding debut, he showed a lot of composure in a cauldron like that
John Connolly on Berrick Barnes
"They gave us the hard match we wanted. I was delighted with the lead at half-time but I was disappointed with the second half.
"We loosened up considerably and gave Wales opportunities to come back into the game."
The Wallabies had to overcome the absence of fly-half Stephen Larkham, who will undergo surgery on Sunday to determine the extent of the knee injury he sustained in training.
They also lost captain Stirling Mortlock at half-time to a shoulder injury that is likely to keep him out of next week's game against Fiji.
Connolly drafted in rookie Berrick Barnes in place of Mortlock and was delighted with his contribution.
Worst case scenario I won't be back before the semi-final
"It was an outstanding debut," he said. "He showed a lot of composure in a cauldron like that."
Wales fly-half Stephen Jones was also full of praise for his young opposite number, saying:
"I thought he was outstanding. His kicking to touch was superb and he got the line going and made the break for the first try."
Barnes, 21, could have a large part to play in the tournament, Australia set to learn more about the extent of the injury suffered by 102-cap fly-half great Larkham on Monday.
"Best case scenario I'll get 20 minutes against Canada; worst case scenario I won't be back before the semi-final," said Larkham after the Wales game.