It should have been one of the greatest moments of her career. 

Standing on the sideline of Lang Park in Brisbane, her muscles warm and her socks pulled tight to the knees, Kyah Simon was ready to enter the field for the Matildas in the dying stages of their Women's World Cup quarterfinal against France.

She was nervous — an unusual feeling for the 32-year-old, who'd played in plenty of big games before — but she knew exactly what she was there to do.

Having worked her way back from a devastating knee injury, the forward was the shock inclusion in Australia's final 23-player squad for the tournament.

She'd missed the 2019 edition in France due to another injury and thought this World Cup on home soil could be her last, so she pushed herself to the edge of what was "humanly possible" to be part of it in any way she could.

She made the squad cut-off — an achievement she said was "miraculous" — and felt that everything was on track to get her first minutes for Australia in over a year.

When asked about her selection, head coach Tony Gustavsson had said that Simon's experience would be valuable if the team ever went to extra-time or faced a penalty shoot-out. It was a role she wasn't used to, but one she would embrace if it meant she could be part of something special.

However, while she was in camp, some soft-tissue injuries flared up. She trained separately from the main group, received targeted individual treatment, and simply hoped that she'd wake up one morning and the pain would be gone.

"Whether that's related to the knee or not, you'll never know," she told ABC.

"It possibly could be because your body's cutting corners and compensating for other things — it's hard to say whether that's related or unrelated — but it's not how I envisioned my World Cup campaign to be.

"And the last thing I wanted to do was bring attention to my situation, because there's already noise — and there's always going to be noise, it's a World Cup — but what amplifies it is if you have another couple of injuries and there's suddenly more focus on you, when otherwise you might just fly under the radar."

By the time the France game arrived, though, her niggles were manageable enough that she felt ready to take to the field for the game's final few minutes.

And so there she was on the sideline in Brisbane, visualising the penalties they had all been practising at training, thinking back to the big goals she had scored for the Matildas over the years: the 2010 Asian Cup, the 2011 and 2015 World Cups, the 2016 Olympics.

She knew she could be the big-moment player everyone expected her to be.

But that moment never arrived.

After some conversations among the coaching staff, who were tossing up the risks of other injuries and the flow of the game, they decided to keep Simon on the bench and let the players already on the field see out what became one of the most-watched television events in Australian history.

And while she had a front-row seat to the drama that unfolded, Simon was also flattened that she couldn't be out there with them.

"I've never been in the position where I've put on a Matildas jersey and never actually taken part on the field," she said.

"But I just tried to be the best supporter and fan of the girls that I could be in any moment, to bring the vibe or help with the energy.

"I think in major tournaments, those finer details are sometimes what gets you across the line or can make you fall short. And Tony is very much for that attention-to-detail part of it.

"So I knew that every time I was in and around the squad, the way I carried myself, that was going to impact the team. The team is always going to come first in my eyes, and I'm going to do whatever I can to support and help them be successful."

She was also worried.

Knowing that her position in the squad had been criticised, especially after the calf injury to Sam Kerr on the eve of the tournament, she expected there to be another wave of noise now that she wasn't able to take part in the exact scenario she had been chosen for.

"It was really hard for me to keep quiet," she said.

"Tony copped a lot of scrutiny for that, but one thing that I really respected him for was that he stuck by his guns and said 'I've selected Kyah for a number of reasons,' and he was very open and transparent with me about that as well.

"But the thing that trumped everything for me is I got myself back to the fitness level that I needed to get myself selected. That's the thing that I'll hold my head high and say that I was able to do that: to defy the odds.

"So I always tried to put things in perspective: that I wasn't meant to be there, I was never guaranteed a spot to be there, and that I'd overcome so much just to get myself in a position to be selected, which was a weight off my shoulders. Everything else was a bonus."

Simon may have missed out on playing in what could be her last World Cup, but she's adamant that her career is not over yet.

Having seen out her contract with Tottenham Hotspur in England, the Sydney local has returned to A-League Women for the first time in four years as the big-name signing for the Central Coast Mariners, the club that handed Simon her professional debut back in the league's first-ever season in 2008.

She joins a number of other Matildas including Cortnee Vine (Sydney FC), Tameka Yallop (Brisbane Roar), Lydia Williams (Melbourne Victory), Chloe Logarzo (Western United), Emily Gielnik (Melbourne Victory) and Elise Kellond-Knight (Melbourne Victory) who have signed for Australian clubs to help boost the profile of women's football in the afterglow of the World Cup.

For Simon, this full-circle moment is also about reconnecting with her country, her family, and herself.

She is still on the long road to full recovery from her injuries, and likely won't be available for the opening round that starts this weekend, but hopes to take the league by storm once her body allows her to.

"Shortly after the World Cup, I was tossing up my club future and where I wanted to be, but what dictated my decision was what I felt like I needed on and off the park," she said.

"First and foremost was the medical staff and the support I know that I get here in Australia. I think it's second-to-none compared to anywhere else in the world, and coming off such a major injury, I needed to put that above any aspirations to play overseas.