The transformation of Matildas goalkeeper Mackenzie Arnold

It is the final game of Group B at the 2023 Women's World Cup.

Australia is in a must-win match against Olympic champions Canada and, while the tournament co-hosts are ahead, momentum is slowly starting to shift in the North Americans' favour.

Canada flyer Deanne Rose shapes up to take a shot. She only has to place the ball beyond Matildas keeper Mackenzie Arnold and the match will once again be in the balance. Her shot is low, aiming for the corner of the far post. But Arnold makes the save, unconventionally with her feet, and Australia maintains their clean sheet.

It was a small moment, particularly in what would go on to be a resounding 4-0 victory for the Matildas, but it spoke volumes to the growth of Arnold as a goalkeeper. This time last year, the West Ham United shot-stopper was widely considered in Australia's top three keepers -- but few had her pegged as the Matildas No. 1.

In a way, Arnold had made a national team career out of being the backup. She'd gone to two World Cups, two Olympics and two Asian Cups. In those three tournaments, she has made zero appearances, one appearance, and three appearances respectively. For whatever reason, Arnold had always been a good player, but couldn't translate her club form to the national team.

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That all changed at the start of 2023 when she started every game at the Cup of Nations and would go on to be named player of the tournament. Subsequently, Arnold started for Australia in friendlies against Scotland and England, keeping a clean sheet against the reigning European champions. All of a sudden, heading into a World Cup on home soil, there had been a seismic shift in the Matildas keeping ranks. The Gold Coast-born keeper recognised the shift when asked about her selection.

"It's more so the position I'm in within the team now, compared to last announcement -- I think it was sort of a lot more real," Arnold told media on the day she was confirmed in Australia's 23-player World Cup squad.

"Previously, I would go in thinking: 'You are going to be the third goalkeeper, you won't play.'

"But this time was a little bit different."

What had changed? How did Arnold go from being good enough to be selected, to good enough to start? The answer, according to long-time teammate and centre-back Clare Polkinghorne, was simple.

"Macca is in the form of her career, and I think just she has belief in herself and confidence in herself -- which we all had in her, but she was probably lacking herself," Polkinghorne said.

Gaining confidence in oneself is easier said than done. And it feels like an even harder task for a goalkeeper whose high points on the pitch are the stuff of legend and whose low points are magnified to an overwhelmingly large size.

Pre-tournament, Arnold, braced with a solid few months of national team football behind her, spoke openly about the changes she has made and how they have fueled this transformation.

"I'd previously say I would dwell on [mistakes], for sure," she admitted. "Being in the position I was in, I was so worried that I was going to give the coach or my teammates a reason to be like: 'That's why we don't play you,' if that makes sense."

For anyone who has ever dealt with self-doubt, it makes perfect sense. But the switch from Arnold worrying, to giving herself a break, was one she needed to make by herself and for herself -- though West Ham played a role in the change.

Arnold explained that before, during games, the fear of making a mistake would loom over her like a cloud. She would criticise her own decision-making and choices harshly and think to herself: "Oh s---, what have I done?

"And then I would watch it back and I'd think it wasn't even that big of a deal. So I think doing that has really helped me to just let those mistakes go and just maybe look on it after and sort of dwell on it then. But it's definitely taken a little work."

The change feels like a simple one, but it's a change that needed to come from within and that's what makes it hard. Arnold already had the backing and belief of teammates and coaches continuously selected her because she was good enough.

"I think taking my form from West Ham to national team was probably the most important thing for me, because for some reason, I could always perform at club level, but I've never brought it into Matildas," Arnold said. "So once I started doing that, and it all started falling into place, I think it got me into the mindset that I needed to be for the last 15 years.

"Now I feel good. I feel confident."

The change has been evident during this World Cup campaign. Before the incredible save to deny Rose, there was a miscommunication between Arnold and Alanna Kennedy which led to an Asisat Oshoala goal in Australia's shock 3-2 loss against Nigeria.

A younger Arnold might have become consumed by the error, letting the fear of a mistake and its ramifications stop her from playing her game. Now she is able to look at the error, take what she needs from it and move on, without fear that she'll be toppled from the pedestal.

Heading into Monday's round of 16 encounter with Denmark, Arnold is the Matildas' undisputed No. 1 and has backed that up with two clean sheets at the tournament and a string of brilliant saves. Her profile has risen thanks to the consistent game-time, and she is facing the prospect of being a role model for the first time in her career head on.

"To be honest, I don't think I've ever really looked at myself like: 'You're a role model,'" Arnold explained. "Even thinking about stuff that I post [on social media], I never really think about it properly ... but you have so many eyes on you.

"Even just seeing Arnold jerseys in the stands, it's probably something that I'm not really used to as well coming from the previous years when I haven't really been a main player. So it's been cool.

"Just being a little bit more noticed in the shops and stuff, which all the girls are probably used to that. But for me, it's sort of just come recently, and it's been nice, it's made me realise how much of an influence we do have on that younger generation."

While not deliberately using that influence, Arnold has already made an impact just by sharing her life, most notably, her recent decision to finally get hearing aids. But, all in all, Arnold is enjoying the moment and embracing the experience that has been beyond her wildest dreams.

"I didn't even really know what to expect coming into this home World Cup," she said. "And it has just been unreal, I can't even put it into words, especially like the feelings that I get when the girls score is something that honestly I can't even put into words.

"It's been something that I would never even imagined. And I remember being asked about what I'm going to expect heading into the World Cup. And I said: 'Oh, yeah big crowd, family and friends, whatever.'

"But looking back now, I could never have said what has happened. It's been unreal."