And Warburton, who missed the third-place playoff through suspension after the red card he received in the semi-final against France, admitted that there was plenty of room for improvement in time for next year's internationals.
"At least this result will give us a bit of a kick up the backside," he said. "We know now we've still got a lot of work to do.
"I think the standards have dropped a bit from the World Cup. We really felt we could build upon our performances out in New Zealand and get a big scalp at home against Australia.
"That would have been huge for us, so it's a massive shame we didn't get that win. We felt our fitness levels had dropped a little bit from the World Cup.
"We couldn't keep that intensity up for 80 minutes and we didn't react very well to the yellow card."
Wales conceded three tries in the space of ten second-half minutes after full-back Leigh Halfpenny was sin binned for tackling James O'Connor without the ball but Warburton refused to lay any blame on the Blues flyer.
"It wasn't Leigh's fault at all," said Warburton. "He saved us seven points, but we conceded 21. We should never have conceded 21 points with a sin-binning like that.
"It was disappointing really. We didn't react properly, our heads went down a bit and they were so clinical then it was really hard to defend against.
"We need to learn to react a bit better when that happens. We practice in 14 men situations in training."