"We need to rethink a few things, that's for sure, and that will be done," Whatmore told reporters in Colombo without elaborating further.
"We have had some reasonable performances against Australia just recently. But they have played very well in the last three weeks or so, in the warm up games and also in this tournament. So it will be a good test.
"Any one of three teams can still make it. It's fantastic for them (organisers) and spectators, not good for us," said Whatmore.
If Pakistan lose to Australia, the 2009 winners can still qualify for semi-finals provided South Africa beat India in the final Super Eight game with a lower net run rate.
India and Pakistan have each won one of their two Super Eight matches.
"There is no doubt in this format, momentum and confidence are really big factors," Australia captain George Bailey told reporters.
"We are really confident going into the last game on the back of how we have been playing."
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