Many fancied his side to be comfortably challenging for a top-four spot this season after some decent-looking signings and a solid debut campaign of bedding in.
Suddenly, they find themselves languishing in 11th place in the table.
Impressive wins against Manchester City and Aston Villa served the purpose of papering over some worrying cracks to a point, and Spurs fans may have been awash with love hearts in their eyes once more after their ferocious start against Chelsea on Sunday, where they took an early two-goal lead against an in-form Blues side at the Tottenham Hotspur Stadium.
But the tale soon came crashing to a halt - somewhat predictably, given the history of the fixture.
Silly penalties handed to their London rivals by Yves Bissouma and Pape Sarr, plus some basic schoolboy errors in the backline and a fading impetus in attack after conceding their first of the evening meant that the only wind left in Tottenham's sails came from the lingering remnants of storm Darragh as the cold winter evening wrapped up in N17.
The 4-3 defeat to one of their closest rivals meant Spurs have now lost seven out of their 15 league games this season, their worst-looking L column since the dark days of David Pleat a little over two decades ago.
During Postecoglou's tenure, Spurs have scored 105 goals but still conceded 80. In all competitions, he has an overall win percentage of just 50.79. That is not pleasant reading for anyone involved with the club.
Nearing the danger zone
Jose Mourinho was allowed 58 Premier League games under chairman Daniel Levy before his unceremonious sacking, while Antonio Conte was given 56 matches. Two world-class coaches who had every right to be given time to buck Tottenham's trophy drought and who, in hindsight, got a lot out of an otherwise lacklustre squad barely clinging to its status as one of the so-called "big six."
Both have also had plenty to say about the inner workings and genuinely defeatist attitudes of the club (seemingly pointing fingers directly at Levy) that remain very hard to argue against.
Much has been spoken about Levy's fiscal triumphs and economic successes off the field, with Spurs consistently churning out table-topping numbers in terms of sustainability and profitability.
But shiny new stadium aside, Spurs have consistently been a side in transition for some 25 years of ENIC ownership under the chairman and club owner Joe Lewis, bar perhaps some brief periods of respite for supporters under the guidance of Harry Redknapp and Mauricio Pochettino.
You would require more than the biological norm of two hands to count the number of fan protests against the way the club has been running in recent years, both pre and post-glorious new stadium.
All of those have and likely will remain fruitless until the club is eventually sold to yet another ludicrously rich financier with questionable human rights records or ethically dodgy tax avoidance schemes.
But all that aside, Postecoglou should not be shielded from criticism.
Ange's blue and white army
The Australian coach has had three transfer windows now with which to spend money and money he has spent.
Dominic Solanke has come in and done well. He looks like a sensible buy at a club record £65 million, while the £45 million Brennan Johnson is still going under the radar despite his impressive numbers.
Micky Van de Ven was also an excellent piece of business, albeit not necessarily under Postecoglou's watch.
He knows what he wants and has made little complaints about the depth of his squad, which on paper - while one of the youngest in the league - is one of the better teamsheets any Spurs manager has had since they reached the Champions League final in 2019.
Transfers are not the issue, in fact, Spurs look in decent shape for the future with the likes of Archie Gray, Lucas Bergvall and Mikey Moore looking promising.
But Ange won the role based on his style of football first and foremost, and his ability to win trophies off the back of it.
Herein lies the problem: With all due respect, the Premier League is not Japan's J-League. It is not the Scottish Premiership. It most definitely is not the Australian A-League.
What should be even more evident is that you are not at a club that hands down has the best, almost unchallengeable squad in that league, as has been the case with his more recent successes.
This is not to say that Postecolgou is an idiot, not by any stretch. The 56-year-old is a man of the world, boasting an intriguingly different managerial CV that has seen him take in footballing flavours from across the globe, and he's had success everywhere he's been, especially as he himself has noted by declaring he "always wins something in his second season."
It's a remarkable thing for him to have said, and it's likely going to come back to haunt him, but it's a good example in pointing to the slightly over-the-top, potentially arrogant confidence of the coach.
Risk versus reward
With respect to the coach, it's fair to say his appointment was on the riskier side when he was brought in by Levy last year.
Aside from perhaps Manchester United, Tottenham is arguably the toughest job in England right now, maybe even Europe.
Whilst not historically a trophy-laden club, Spurs are a strange case study in that, due to their financial success off the pitch and consistently finishing about where they should be within the top six or seven in the league for a couple of decades, they're expected to be serial winners of most competitions they enter.
It's slightly unfair when you consider what they're up against, the competition they face in the market, and not least the competition for places domestically.
Still, they've gone nearly 17 calendar years without a trophy, and some 33 years since they won anything other than the League Cup.
This is now becoming almost unacceptable, but it's also created a strange situation where Spurs are effectively in a Football Manager-style 'challenge mode', where someone (à la Mourinho, Conte) can come along, take the wad of cash and try and do something that so many others have failed to achieve: Win something for Tottenham.
That's the remit here, and Ange Postecoglou is currently failing it because he's failed to accept that what has worked in lesser leagues can not and never will work at the top end of English football.
There is no other league like the Premier League. Nowhere else in Europe can you find an elite-level competition where a star-studded side like Manchester City can be comfortably beaten by a Bournemouth or Brighton in back-to-back weeks. No result is a given. Every point is fought for, no matter how big the gap is between wage bills.
Every match is about weighing up risks across the pitch, and no two games should be treated the same. Who honestly thinks, when taking Tottenham's squad on an honest footing, that the same tactic that might work in a 4-0 home drubbing against a struggling Everton will work on an away day at Newcastle, who treat St. James' Park like an actual fortress?
Blind optimism
Postecoglou is a stubborn manager. He says it all the time: "This is the way we play", "We're not going to change", "It is what it is, mate."
Unfortunately, he does need to change - and fast - or he risks losing all grip on his side's competitiveness this season and simply becoming another statistic in the Tottenham managerial merry-go-round of rinse and repeat.
Injuries. Yes, he's had some injuries to contend with this campaign so far. Injuries are always a lingering threat for every side, no matter how stacked, and particularly at this point in the season. This is even more reason to adapt your system to fit with what you actually have.
On a good day, Spurs are nothing short of breathtaking to watch. Their football can be sublime, and even the fiercest of rival fans can't help but admire it and even enjoy watching it unfold.
The practice of 'we'll score one more than you' while attempting the flick-ons, intricate passing, and bold, adventurous attacks are a joy to behold.
But we're all human, and we all have our off days, so you need to have a plan for when you're not at your best.
How do you do that? You prioritise your strengths and focus on doing what needs to be done in order to get the results.
No great title-winning side has ever won the Premier League with 38 games of pure footballing perfection.
What you mustn't do is persist with the same old method time and time again in the hopes that it will always yield positive results. That's not too far removed from the actual definition of insanity. At best, it's pointlessly blind optimism.
Fans aren't always fickle
Postecolgou is also teetering into dangerous territory now with large sections of the Spurs supporters.
They were booed off after letting a relatively comfortable-looking 1-0 lead slip in the dying embers against Fulham, costing them two valuable points.
Perhaps booing a side off after a 1-1 draw against a dangerous London rival is harsh, but they weren't booing that specific performance per se. They were booing the infuriating levels of inconsistency that really shouldn't be happening. There will be much tougher runs of games to come in the season still.
However, the following week was a dismal showing that ended with a thoroughly deserved 1-0 loss against Bournemouth, resulting in the Australian approaching away fans with his chest puffed out, seemingly ready to invite every single one of them outside to the carpark for a bit of afters.
This is not a good look, and it smacks of pressure starting to cook on the Aussie's gruff grill.
Fans know what he's trying to do. They're not stupid. They love the club like anyone loves their partner, no matter how toxic the relationship might get.
But those away fans in particular are the same fans travelling to every game home and away, week in, week out. They're the ones following the team around the country, forking out on either ridiculous train tickets or petrol prices.
They're spending a ton per head just getting public transport to Tottenham High Road and feeding themselves for home matches, not to mention the actual ticket cost itself, which are some of the highest ticket prices in the country - but for what, exactly?
Postecoglou should not forget that a very real, impactful cost is involved for these dedicated fans, even if he doesn't have to worry about how his monthly wages will cover all the rent and bills.
Plus, they're a tired bunch. Tired of the same old excuses from managers, players and the chairman.
They're tired of always being forced to reminisce about how they nearly won a Champions League or nearly won the Premier League once.
They're tired of being in transition and looking to the future only for the players to be sold when they hit their prime. They're tired of the same old, predictable mistakes.
Plan B
Postecoglou, while not solely to blame by any stretch, needs to address the criticism that he's getting from literally every angle: He needs a plan B.
He (or perhaps more specifically 'Angeball') has already been found out at this level. While glorious on a good day, Spurs are wide open and easy to play against on a bad day - and that's with a fully fit squad to boot.
It takes a very certain type of arrogance to waltz into the best league in the world with no prior experience at that level or in that country and refuse to accept that you might be wrong about your 'philosophy'.
No great manager has ever stuck to one single, solitary principle.
There is no chance your Pep Guardiolas, Sir Alex Fergusons, Jose Mourinhos or Jurgen Klopps would ever have found the levels of success they did without learning to adapt to situations as a team and planning for every conceivable outcome. That's a burden all great leaders have to shoulder.
It takes a much bigger character to accept when they are, in fact, the one who needs to change.
Nearly all of Tottenham's fanbase wants to see the likeable manager with exciting ideas succeed. The last thing they want is to see him sacked too soon and for the miserable cycle to begin from scratch once again.
By all accounts, the players themselves are happy with him at the helm and are determined to put things right before any mounting pressure becomes too great.
But whether it's freshening up his training methods, holding some of his backroom staff to account, or simply looking in the mirror at whether he's let last year's smoke blowing get too far up his pipes, something has to change.
Otherwise, before too long, he'll be just another Juande Ramos, Christian Gross or Andre Villas-Boas.
