Wales has emerged from a period of tumult to sit top of Pool C thanks to wins over Fiji and Portugal.
They are again led by a familiar face in New Zealand coach Warren Gatland, who answered an SOS to replace compatriot Wayne Pivac late last year.
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Wales was reeling both on the field and off with a financial crisis among the provinces and allegations of racist, homophobic and sexist bullying within the national union.
Those issues haven't completely gone away but Gatland's presence has allowed a feeling of calm and certainty among a new-look squad now missing the likes of Alun Wyn Jones, Justin Tipuric and Ken Owens.
And winger Rees-Zammit confirmed that confidence levels are "high" for the crucial Australia clash.
"Two wins. And when you don't get perfect wins there's always a lot to improve on," Rees-Zammit said.
"That's great. We need that progress."
The pacy 22-year-old caused a stir with his try celebration against Portugal, unleashing a Cristiano Ronaldo 'Siuu' for the crowd.
"Ronaldo is my favourite player," Rees-Zammit said.
"I wear his boxers and I dress like him. And I thought why not do his celebration as well? A few of my mates back home wanted me to do it.
"They're massive football fans and obviously we don't play Portugal very often. So I said if I scored I'd do it for them."
There was some blowback on social media from viewers who believed Rees-Zammit was trolling the Portugese.
"It wasn't meant to be offensive or anything," he said.
"I absolutely love Ronaldo, he's my idol and I thought why not do his celebration?"
Wallabies coach Eddie Jones boasts a 11-5 career win loss record against Wales, across Tests with Australia, England and Japan.
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Understandably then, Wales assistant Jonathan Humphreys was respectful of the challenge that Australia would present.
"It's going to be as hell of a game," Humphreys said.
"There's going to be a lot riding on that. I thought Australia were excellent in the first game (against Georgia).
"It was always going to be a massive game. It will be interesting to see how they come out. He's (Jones) always got something different in his game. But Eddie is not playing in the game. The players he has available to him right now are a hell of a squad.
"We're in a pretty good place but we know we need to improve and get better if we are to do the job against Australia."
The game will kick off at 5am AEST on Monday.