Australia went into that tournament with only nine of the 23-man squad having reached double digits in the number of caps they had won.

Only four - Tim Cahill, Mark Bresciano, captain Mile Jedinak and Matt McKay - had played 30 or more times for the national team. Fourteen of the 23 were aged 25 or less.

The theory was that Postecoglou would seed his squad with talented, ambitious young players who would learn the Ange way and be battle-hardened not just for the Asian Cup but to make an impression in the World Cup in Russia four years hence.

Postecoglou is no longer there. He famously walked out just after his team had struggled to qualify, scraping in by beating Syria and Honduras in play-offs.

And many of those players upon whom such high hopes were invested are not there either.

Some fell by the wayside, a handful retired, a couple were surprisingly dumped by Postecoglou's replacement, Bert van Marwijk, and some were overlooked through a combination of form or injury.

Postecoglou's gamble worked well for the Asian Cup, as Australia won the title in extra time with that dramatic victory over South Korea.

Four years on, it's interesting to see how many of those who looked as though they would be the bedrock of the Socceroos for the forseeable future actually have become key players.

Massimo Luongo, now 25, is one of only six from the 2014 World Cup squad to have survived to Russia: he is joined by greybeard Tim Cahill (now 38), Mile Jedinak (33) Mark Milligan (32), goalkeeper Mat Ryan (26) and forward Matthew Leckie (27).

Of the Asian Cup winning squad from January 2015 the same sextet, plus a handful of others, have made it to Russia. They are the 26-year-old centre-back Sainsbury, who probably would have been in the squad in Brazil but for injury, Kruse (ditto), Tomi Juric and Aziz Behich.

It's surprising, with the benefit of hindsight, to think that the man many now regard as the heartbeat of the team,  midfielder Aaron Mooy, was not in either squad such a short time ago.

The shaven-headed Huddersfield star was, in the winter of 2014, a long way from Brazil. He was rebuilding his career and making the move that was to be so central to his development, leaving Western Sydney Wanderers and joining Melbourne City.

Despite a great start with City in the 2014-15 season he was overlooked for the Asian Cup squad, Melbourne Victory's current midfielder Terry Antonis  probably getting the nod ahead of him.

Perhaps we should not be surprised that there has been so much change. Football is a dynamic environment, and players who might look terrific at 23 have often petered out by the time they are 27 when they might be expected to be at their prime.

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The reverse is also true. Mooy, now 27, is the best example in the current squad of how a player can improve with age and maturity.

Still, given Australia's difficulty with scoring goals, it's tempting to wonder how things might have been had some of the attacking players who were 25 or under in Brazil had gone on with the job.

Adam Taggart started up front against Spain. At 21 he looked to have a bright future. But things turned sour when he moved to Fulham and Dundee and he has spent the past couple of seasons in the A-League with Perth Glory. He has now joined Brisbane, and at 25 still has time to come back into international recognition.

Ben Halloran spent five years in Germany with Fortuna Dusseldorf and then Hedenheim before switching to J-League club V-Varen Nagasaki this year. He has rarely been sighted at international level since coming on as a sub against Chile in Australia's opening 3-1 loss in 2014. He, too, is just 25, so could bounce back.

In 2014 youngster Tommy Oar looked to have the world at his feet. He was playing in Utrecht in the Dutch Eredivisie and was a regular in Postecoglou's line-ups. But his form tapered off and even during a season in the A-League with Brisbane he could not recapture former glories. He is currently playing in Cyprus. Aged 26, he is not past it, but looks to have had his time.

James Troisi is the closest of that bunch from 2015 to have made Brazil. The Victory forward was in the group training in Turkey but was one of those cut when the squad was trimmed to 23. He is now aged 29, so his time may have gone.

Given Australia's scoring woes, van Marwijk would have loved one of those to have progressed. His successor, Graham Arnold, will be hoping that the likes of Andrew Nabbout, Dimi Petratos, Daniel Arzani, Jamie Maclaren, Rogic and Juric from the current squad fare rather better over the next four years.