Australia's shaky performances in their last two triangular series one-day matches have boosted England's and New Zealand's belief that the home side is beatable.
The Aussies are still on course for an unbeaten summer and their narrow two-wicket win over the Black Caps at the Sydney Cricket Ground on Sunday was their eighth successive victory in one-day internationals.
But New Zealand arguably cost themselves an upset win with three fielding blunders.
Australia's uncertain performances, particularly their top order frailty in the last two games, have left New Zealand captain Stephen Fleming convinced that the right game plan can undo the World Cup favourites.
England seamer Jon Lewis, who claimed four wickets against the Australians last Friday, echoed Fleming's sentiments and said his side believed they could beat Australia.
"They're definitely not unbeatable," Lewis said on Monday in Adelaide ahead of his side's clash with the Kiwis.
"They're a very, very good side and full of very good players, but I think we can beat them definitely. The game against Australia on Friday is definitely a game we can win."
"The guys are very confident, we've got great spirit in the camp and we're all keen to win a game against Australia."
"They're playing good cricket at the moment, but we need to just keep fighting, scrapping because we've really fought hard in the games we've played, and if we keep scrapping we will turn a result around against them," he added.