The 57-year-old, who is expected to be confirmed as Tottenham boss, has enjoyed success pretty much wherever he has coached over the last 26 years.
Although raised in Australia where oval ball codes rule the roost, Greek-born Postecoglou is a passionate football man with firm, unchanging ideas of how the game should be played.
"My vision is that I want to play football everyone talks about and with that, hopefully, we will have success as well," he said in 2020 when explaining how he built a championship-winning team at Yokohama F Marinos.
That 2019 success in the J-League, the toughest league in Asia, was by no means his first title but gave him enough credibility to land the job at Celtic in 2021.
His appointment at Parkhead was widely mocked, with former Scotland striker turned radio pundit Alan Brazil leading the charge when he scoffed that the news must be "a wind-up".
Brazil was happy to eat humble pie 11 months later after Celtic won the League Cup and Scottish Premiership title, likening the move to Arsenal's appointment of the little-known Arsene Wenger in 1996.
Three more trophies followed this season at Celtic and the treble was wrapped up on Saturday when Inverness Caledonian Thistle were beaten 3-1 in the Scottish Cup final at Hampden Park.
"When I came here ... the opportunity for me was that the team had been dismantled so... I could really build a team in the image of the football I wanted to play," Postecoglou said.
"The risk was, if I got it wrong, it would be a disaster. Fortunately, I got it right."
Postecoglou's reputation for rebuilding teams and getting them to play in an adventurous, attacking style was built in his first job in the Australian top flight at Brisbane Roar.
Brisbane won successive A-League titles in 2011 and 2012 and he had started a similar rejuvenation project at Melbourne Victory when the Australia job fell vacant.
Eight months later, he led the Socceroos to a winless but not entirely unworthy campaign at the 2014 World Cup and the following year secured Australia's first major title at the Asian Cup.
Postecoglou led the Socceroos to qualification for the 2018 World Cup but, frustrated that the Asian Cup triumph had not proved the watershed he had hoped for Australian football, quit before the finals and headed off to Japan.
There he expounded on a football philosophy grounded in the 'Total Football' concept developed by Rinus Michels at Ajax Amsterdam in the early 1970s and built on by Johann Cruyff at Barcelona.
"Total Football is when you have the ball and everyone is involved, and the extension of that for me is that when you don't have the ball everyone is involved as well," Postecoglou added in that 2020 press conference.
"Some teams press aggressively but don't have the ball much and play direct, and other teams have the ball but don't press. We try to do both, which is not easy.
"We're trying to play our game and the key to it is it looks simple. And if it looks simple it means that it's probably very complicated."
Engaging and articulate, Postecoglou can be thin-skinned when he thinks criticism is unwarranted, or when he feels the critics are unqualified to offer it.
"I've been called egocentric. Selfish. There have been calls for me to get sacked. But you know what? I'm still here. I won't change who I am and what I believe in," he said before a 2017 World Cup qualifier. "It doesn't hurt me."
