Forest didn't play too badly at St James' Park on Sunday but the 2-0 loss to Newcastle -- a fifth defeat in seven winless games for the Australian boss in a luckless four-week reign -- only makes his position even more precarious.
Yet Postecoglou was, as ever, adopting a defiant face as he declared he was relishing the challenge of extricating Forest from their predicament.
He even referred back to distant memories of his very first managerial job back home in Australia, when he took the reins of Western Suburbs in Melbourne, to explain his love for a scrap.
"I started in Australia when I was 32 years old in semi-professional football and I'm here in the Premier League at the age of 60. Do you reckon I lack self-belief or don't like a fight?" Postecoglou told reporters in a passionate post-match address.
"I didn't get here because of my connections. In fact, I've picked fights. I have, even in the schoolyard, I've picked fights with people who I knew would beat me up. That's the kind of person I am, so that's fine.
"If people want to make an assessment of me after three-and-a-half weeks in which I've had six or seven games, there's nothing I can do about that.
"But at the same time, there's nothing wrong with things being tough. That's okay. I'll say it a million times, I did have an option. I could have been sitting on the couch watching the game today, and not be in the middle of it.
"I'd rather be, much rather be ... I love a fight. So it's a fight, so it's a struggle - so what? That's okay. Now, if people outside don't think I'm the right person, or even internally don't think I am, it makes no difference for me."
Postecoglou now goes into an international break, and says he "expects" to be talking to owner Evangelos Marinakis about "what we have embarked on here, where we are at and what we are going to do" following the worst start by any new Forest manager in a century.
"The results will come," he insisted after Newcastle had won through second-half goals from Bruno Guimaraes and Nick Woltemade just three days after Forest's damaging Europa League home defeat against Danish side Midtjylland.
"In the meantime, it is a struggle and a fight and there is nothing wrong with that. We don't want things handed on plate we have to fight for it, I have fought for things all my life," said Postecoglou.
"I don't get why people think it is a burden but I love a challenge. What I have seen and felt in this period is that we are heading in the direction I want us to."
Yet things look bleak for Postecoglou, who even curbed his more enterprising instincts, adopting a more defensive approach on Sunday yet still couldn't stop his side leaking two more goals, which makes it 15 now conceded in their seven-game winless streak.
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