That’s the unpalatable prospect facing the former Socceroos coach overnight in London, where - in the hearts and minds of a sizeable number of Spurs fans - beating Manchester City at the Tottenham Hotspur Stadium would be an unmitigated disaster.
 
The notion of wilfully giving the Gunners a leg up - and the attendant connotations of endless bragging rights and an eternal banter weapon - is simply too much to countenance for many Spurs followers.
 
For Ange to be complicit in that potential outcome would cast him forever as an aider and abetter of a bitter enemy.
 
Future footage of Mikel Arteta and his team on a champagne-soaked open-top bus tour through the streets of Islington is the ultimate nightmare for those in the nearby white quadrant of north London.
 
With all this mind, and Postecoglou unwittingly caught in the middle of an unseemly internecine spat, the scenario is this: Arsenal lead City by a single point with two games left.
 
Beat Spurs at a venue where they have yet to win in the league under Pep Guardiola and City will be on the brink of an unprecedented fourth successive EPL crown going into their final day fixture at home to West Ham.
 
If, God forbid, Spurs take a point, or even win, then Arsenal stay at the summit - needing to only overcome Everton at the Emirates to take out their first title in nearly two decades, even if it might ultimately come down to goal difference.
 
To further complicate matters, Spurs need to take maximum points from City and then away at Sheffield United, and hope Aston Villa slip up at Crystal Palace in their last match, to have any hope of leap-froging them for the final Champions League spot.
 
All of which leaves Postecoglou in an invidious position in which, to some at least, he’ll be the villain, no matter what the outcome.
 
Whilst social media is ablaze with Spurs fans rooting for City, whilst casting accusatory glances in Postecoglou’s direction, Arsenal devotees are begging their foes for a favour.
 
Doing his best to rise above these tribal drumbeats, Postecoglou isn’t planning on instructing his team to roll over.
 
“You think the majority of our fans are not going to want us to win? I don't see it that way. I think the majority of our fans will create the atmosphere they always create at our games," the Spurs boss said.
 
“We've got a game of football to win and that's what we'll try to do. Man City haven't won it yet and if you think they have, then it becomes an issue because we're rolling out a red carpet for them and I'm not going to do that.
 
"I'm not just going to sit there and watch them win. That doesn't sit comfortably with me."
 
Corralled on whether a significant faction of fans want to lose to stop Arsenal from winning the league, Postecoglou replied: "A proportion of our fans? What does that mean?
 
"What proportion? 50 per cent? 20 per cent? One per cent? That's fine, people are allowed to feel the way they do.
 
"But I think I've been consistent and really strong in my beliefs that it's important for this football club not to look for silver bullets to get to where we want to, it's hard work, it's resilience, it's quality, not to fall for any false dawns - and know what real success looks like: trophies.
 
"Anything else in between, bragging rights, whatever it is, is absolutely meaningless to me or anyone involved with me. We've got a game we want to win."
 
The problem is it’s a match many Spurs fans would far rather lose.