When Postecoglou sat down and gave only a handful of short reasons why he would be leaving his post just seven months before the 2018 World Cup, Gallop was "disappointed". After a month of speculation, side-stepping questions about his future even when approached by his bosses, Postecoglou gave little indication as to his next step, but ultimately the FFA were "supportive" of his need for change, even if they don't know exactly why.

Their best guess is the combination of a number of factors, but even still, they're still guessing at best. Postecoglou did not give much away publicly either and when announcing his resignation on Wednesday morning.

"Overall, sometimes it's just an instinct," he said. "For me it feels like the right time."

Having survived the most arduous qualifying campaign ever experienced by a country in the 88 years of the World Cup, Postecoglou was worn out. Twenty-two games, 29 months and more than 250,000 kilometres travelled took its toll on the coach who made no secret of his desire to take a short break with his family.

"'ll probably need to have a break with the family and just sort of regather my thoughts," Postecoglou said.

"To my three boys, James, Max, Alexi, you make me smile every day and to my beautiful wife ... I left 24 hours after Max was born because we played Ecuador in London ... I'll never be able to repay the sacrifices she's made."

At a meeting on Tuesday, the FFA urged Postecoglou to reconsider quitting and highlighted the fact he would have four months before his next match in charge during the international window in March. That fell on deaf ears. The reason is largely to do with the timing, it's understood Postecoglou is looking to coach overseas with a strong preference of returning to club football. Stepping down in November would help that cause, making him available during January when positions usually tend to open up again in Europe and China.

"I want to coach abroad. Part of me, you know, is pretty keen to get stuck back into club football, working day-to-day," he said. "I mean, I have loved this job. But it's been all-encompassing.

"And the bit I still dearly love is the coaching aspect. So, look, I don't want to be unemployed for too long, obviously."

He has been linked with the top job at Scottish club Rangers. He was understood to be in the running to take charge of Club Brugge. As reported by Fairfax Media, he attracted a lucrative offer from China earlier this year while he is understood to have rejected a chance to coach his country of birth, Greece, in 2015.

On Wednesday, he denied a rift with the FFA. However, it's understood a funding issue surrounding the recent closure of the FFA Centre of Excellence did not go down well. Sources suggest Postecoglou felt "undermined" at times from sections of the media and administrators, however he denied that at his press conference.

He hadn't spoken to the players about his decision, nor several members of the Socceroos' staff. There was seemingly no issue of backing from the players as several took to social media to praise the coach that instilled so much confidence in them and Australian football. He taught them never to back down, to always attack and set in stone a philosophy of wanting to take on every team, even world champions.

That translated to an ultra-attacking style of play and a controversial formation he modified mid-qualification. Last March, he justified the bold decision in order to give the team enough time to have perfected the 3-2-4-1 system come Russia. That he won't be there to see that project through to its completion is understood to have left a sour taste for some within the FFA.

The real sore point, however, is that many of his peers and players aren't much the wiser as to why the first Australian coach to successfully qualify for a World Cup chose not to be there until the end.