Postecoglou was regularly pressed on the high-energy, high-risk, low-compromise style he deployed but said he’d “never move an inch, mate”, in the way he saw the game.

Celtic secured two points from 18 in the Champions League that season.

Domestic dominance was the safety net that trumped European failure. Spurs have no such latitude in the brutal terrain of the Premier League.

Celtic have moved on a little since Postecoglou’s departure and have hit on a style of play that works better for them on the unforgiving fields of Europe.

But Postecoglou’s return will have some fans pondering what might have been had he never received an offer to go south.

Would he have tweaked his natural instincts for the greater good, as Rodgers has done, or would Celtic still be trying to go toe-to-toe with all comers, as they did on his watch, with bad outcomes?

The answer can probably be found in what we’re seeing from the boom and bust that is Spurs – good enough to put Aston Villa, Manchester City and Manchester United to the sword, but also soft enough to cough up goals and points late on in a list of matches they had control of.

As much as Celtic fans loved having him, there’s probably an acceptance now that they needed to lose him to advance in Europe, the real testing ground of a team that has Scottish football sewn up.

Because it’s Postecoglou and because it’s Rangers, half of Glasgow will be white on Thursday. They will always appreciate him and support him, but in the new world Celtic seem to be moving into, the days of lamenting him are over.