"Life's this game of inches," Tony D'Amato says in the 1999 film Any Given Sunday, "and so is football." 

"In either game – life or football – the margin for error is so small: I mean, one half-a-step too late or too early, and you don't quite make it. One half-second too slow, too fast, you don't quite catch it. The inches we need are everywhere around us."

There is one particular game of inches, years ago, that Graham Arnold has been thinking about recently.

It was March of 2019 and he was standing on the humid, sweaty sideline of Phnom Penh football stadium in southern Cambodia. In front of him were the Olyroos, Australia's under-23s team, taking on South Korea in the final qualifying match for the 2020 AFC U23 Championships.

Things were finely balanced; the inches tipping this way and that as the other 10 group games unfolded. Australia had already defeated the hosts and Chinese Taipei comfortably, 6-0 each time, but the permutations elsewhere meant they could not lose this final match.

Striker Nicholas D'Agostino put Australia 2-0 up within 25 minutes, but the Koreans clawed a goal back in the first half before equalising just past the hour. In the final 15 minutes, the Olyroos barricaded themselves in front of Tom Glover's goal, throwing their bodies in front of a shower of shots, trying desperately to protect their single, precious point.

They didn't know it then, but when the full-time whistle blew with the scores still locked at 2-2, the lives of five of those young players – Nathaniel Atkinson, Thomas Deng, Harry Souttar, Riley McGree, and Keanu Baccus – would change forever.

That single point, those single inches, meant the Olyroos qualified for the AFC Championship finals as the best runner-up of the qualifying groups.

They went on to finish third and make it to the Tokyo Olympics – the first time they'd done so since 2008 – with Arnold overseeing a campaign that included a statement 2-0 win over Argentina.

Ten of those Olympians are here at the World Cup, with four of them appearing in Australia's victory over Tunisia on Saturday. One of them, Mitch Duke, even scored the winner.

And just like that pivotal evening in Cambodia, they are once again heading into a delicate final group game that could see their lives ricochet onto yet another timeline.

"Last night, sitting and talking to Harry [Souttar] and Riley McGree and Keanu Baccus […] we started taking about three years ago in Cambodia with the Olympic team," Arnold reflected a few days out from their D-day with Denmark.

Not just these 10, though. There's been sliding-doors moments for all of them, including Arnold.

Thursday morning's game comes 25 years and one day since he last pulled on the green-and-gold as a player, walking off the MCG after that fateful draw against Iran in 1997 that ended his own World Cup dream in what he described as "probably one of the worst moments of my football life".

His coaching career since then has felt like one long project in atonement; an inching ever-closer back to that moment, to seize the opportunity he watched slip through his fingers, and to hold it closer and tighter than ever.

But this World Cup is no longer for him, and he knows it. Arnold's time with the Socceroos is ebbing to stillness.

This, now, is for everybody else, and all he hopes is that the inches he has fought for will add up to something meaningful.

"It's not about me, it's about the game in Australia," he said.

"To leave a legacy is huge. In 2006, what that generation did – and I was very fortunate I was there as assistant coach with Guus Hiddink and experienced that as well – and all the kids that grew up are these kids of this generation. They were ten years of age watching these guys do what they did in 2006. Those guys were their inspiration.

"So it's about putting the game on the map a bit more in Australia. But there's so much more work to do."

Life's this game of inches, and the inches are all around them.

They're in the wriggling penalty save made by Andrew Redmayne, who considered retiring only a few years ago, to win that pivotal play-off game against Peru.

They're in the Glasgow park covered in stud-marks as Aaron Mooy, caught in the crossfire of COVID, ran his way back into Australia's midfield.

They're in the accidental spin of the ball as it arced towards the crown of Mitch Duke, the man nobody thought would make it here at all, to write a new chapter of history in Al-Wakrah.

They're in the outstretched arms of Mat Ryan, who was always told he was too short and too small to be a goalkeeper, swatting away cross after cross after cross.

They're in the impossibly long legs of Harry Souttar, who chose Australia instead of Scotland, as he flung them towards Tunisia's Taha Yassine Khenissi and emerged on the other side, somehow, with the ball at his feet.