IT’S easy to forget how monumental it all seemed back in the summer of 2016.
For those who imagine that the Premier League is Hollywood-made flesh, this was box-office gold.
The most compelling plotline imaginable for football’s great global phenomenon.
Pep Guardiola and Jose Mourinho — Pacino and De Niro, Luke and Darth, Smokey and the Bandit — turning up in Manchester to duke it out with water cannons, spraying hundreds of millions of pounds in a fight to identify the greatest manager on the planet.
Yet for more than two years, all those billboards seemed to have been flogging a bloody great turkey.
The reality was an opening season when both Jose and Pep bombed followed by a second which brought majesty to Manchester City and meltdown to United.
This season began in similar vein — City lording it, United a self-harming rabble with Mourinho taking on his own players. Suddenly, though, in the past seven days, a dark force seems to have awakened.
Suddenly, Manchester United under Mourinho are looking as we imagined they might be.
Bloody-minded, never-say-die, last-action heroes. Ballsing it out in Fergie time, coming from behind to win twice at Bournemouth and Juventus.
Judging by his antics after the final whistle in Turin, Mourinho seems to have experienced one of those mood swings right across his emotional spectrum — from dark, brooding misery to devious, smirking old rascal.
Meanwhile Guardiola’s princes stuffed Southampton and Shakhtar Donetsk in six-goal feasts so lavish that you imagined them repairing to their dressing room to dine on roasted swan.
City are such beautiful bullies on flat tracks but they will need to rely more on their new-found miserly defence — with John Stones and Aymeric Laporte an outstanding young combination — against United.
After clean sheets at Arsenal, Liverpool and Tottenham, can they shut out their resurgent neighbours?
Mourinho claims City are “untouchable” but after a net spend of £315million since he took over, the Portuguese ought to have got closer to his old Clasico foe who has had a net £398m lavished upon him at the Etihad.
Still, all of a sudden the prospect of tomorrow’s derby has us salivating like it’s summer 2016 all over again.
Footballing purists might see it as Saint Pep against the red devil incarnate.
Others will view the accusations of City’s Financial Fair Play chicanery and regard United as the authentic old-school club up against the duplicitous PR arm of a corrupt and abusive Abu Dhabi regime.
Yet no football supporter can argue against the intrigue of a proper Pep team against a proper Jose team.
Of course, United delayed City’s coronation with an extraordinary comeback from 2-0 down at the Etihad in April.
But a week later Mourinho’s men lost at home to West Brom as the title ‘race’ ended in meek surrender.
Mourinho led United to second place their highest finish since Sir Alex Ferguson’s 2013 retirement but it felt joyless.
Now, since another comeback, from 2-0 down to beat Newcastle a month ago, Mourinho is back from the brink with a twinkle.
The personal enmity with Paul Pogba and others won’t have vanished and any hope of a genuine title challenge remains remote. But there is a flickering of the old Mourinho pilot light.
He’s never been full of joie de vivre and his teams have rarely charmed the neutral but United always knew that when they employed Mourinho.
What they thought they were getting — to counter Guardiola’s City appointment — was the anti-Pep.
Yesterday, Guardiola admitted his relief that there is less emphasis on his history of personal bitterness with Mourinho.
He said: “We are both good guys, more than you expect. It’s much better, believe me.”
He did, though, sigh while answering one TV reporter earlier in the week and admitted of Mourinho that “of course, he has his weapons”.
There was a quiet exasperation in Guardiola’s voice and you got the feeling he wasn’t particularly looking forward to taking on his greatest rival. Although, weirdly, Mourinho’s weapons might not be quite as obvious as usual.
United have clicked in the enforced absence of Romelu Lukaku — the sort of target man Mourinho generally employs. Even if the Belgian is passed fit, he may not start tomorrow.
Not that Mourinho will come over all naive and imagine he can out-football City. No Premier League team can do that.
But they will travel across town with class, confidence, hope and doubtless a proper Mourinho gameplan.
So get a bucket of popcorn in. This one might just be epic.