Scotland have performed admirably at the T20 World Cup, batting confidently before being washed out against England before defeating Oman and Namibia to leave qualification in their own hands.
But the final part of the equation is set to be the hardest - taking on and beating a side who can already call themselves Test and ODI world champions and are looking to secure an unprecedented hat-trick of titles this month.
Scotland could still go through in defeat if England also fail to see off Namibia a few hours earlier, but Leask is not counting on anyone other than his own team.
"It's a must-win game, always has been," he said. "I think we knew coming into this game it would be. It's a hell of an opportunity for us. We're still going to have to play our best cricket because we know Australia have got a wonderful squad.
"They've all been in the IPL, they've all been everywhere and, on their given their day, they will dominate sides. They are the best in the world for a reason as a collective unit, but we're going to have to put them under pressure somehow.
"We know that to win the game we're going to have to bat extremely well and with the ball we're going to have to hold our disciplines and bowl really well against a star-studded line-up. We're going to need two or three guys to really put on a show and basically take them on head first.
"I think it would be an incredibly proud moment for Scottish cricket if we did progress to the Super Eights, but let's not beat around the bush. It would be the tough way. We're going to have to bring our A game and take them on."
One weapon at Scotland's disposal is the wily spin of Mark Watt, whose trademark '25-yard' delivery which is sent down from a couple of strides behind the stumps caused a minor controversy against Oman.
He was denied a wicket with the innovative tactic, designed to catch the batter off guard, when the umpire called 'dead ball' to spare Khalid Kail. There is nothing in the laws to prevent bowling before the crease and an undeterred Watt is poised to try his luck against Australia.
"I can guarantee he'll bowl more than one against Australia, let's hope he takes a few wickets with him," Leask said.
"He's taken a lot of wickets with it. I think it's down to the umpire's discretion at the end of the day and they made the right call on that day, but he will be doing it again."
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