There was not a flicker of emotion from Pep Guardiola when the decisive goal which can allow Manchester City to revise their perspective on European football flew in, despatched from a free kick Kevin de Bruyne dipped over the Barcelona wall. But appearances and Guardiola can be deceptive. He will have felt the vast significance.

This was the win which broke the hex that Barcelona have held over this club in these past few years, secured at the sixth time of asking. It was the win rich in irony and symmetry, given that City’s Spanish chief executive and director of football have been creating a corner of Catalonia in eat Manchester since they arrived.

But more than that, it was a result which will allow City to put the struggles and stumbles which this competition has represented in the past. The Champions League has certainly brought them pecuniary wealth - £88.8m last year, as semi-finalists: more even than last year’s winners Real Madrid, UEFA data revealed on Tuesday. But there has been a spiritual deficit. The atmosphere has been dead, the mood malign with the supporters’ boos for UEFA. A full 20 minutes of last night’s game had passed and City fans were still arriving to take their seats.

Guardiola: Man City beat 'the best team in the world'

That moribund spirit was swept away in what happened next. For a time, it was the City that this stadium has been programmed to know – defensively vulnerable, centrally wide open, as Barcelona began to carve them open. But then came the ‘willingness’ which on Monday Guardiola had said several times was necessary: the resolve to chase, harry and induce mistakes. The pressing to death of Barcelona, in the way that they have strangled so many teams. By the mid-point of the second half, Guardiola was making clear his fury with Pablo Zabaleta for playing a 20-yard back pass to his goalkeeper. Forward was the only direction he was prepared to let this side look.

To understand the import of the win, it is necessary to go back to the start of the night because for half an hour Guardiola looked like yesterday’s man.

In Barcelona, they even had a word for the way he used to change things. ‘Guardiolada’ was a tactical innovation used for a big game and for the purposes of that match alone. The general impression provided by the first period was that Luis Enrique was the innovator now; that his is the side which is moving on, leaving Guardiola struggling to harmonize with the same tune.

Manchester City vs Barcelona player ratings Show all 22 1 /22 Manchester City vs Barcelona player ratings Manchester City vs Barcelona player ratings Willy Caballero – 6 out of 10 Couldn’t do anything about the goal but didn’t mess around with the ball when he had it and cleared his lines well. Manchester City vs Barcelona player ratings Pablo Zabaleta – 7 out of 10 Got the crowd up for the game with his performance and watched Neymar well. Manchester City vs Barcelona player ratings Nicolas Otamendi – 7 out of 10 Cut out all the mistakes that have marred his game in his most recent appearances. Manchester City vs Barcelona player ratings John Stones – 7 out of 10 Looked stretched at points when Barca attacked but did well on the whole. Manchester City vs Barcelona player ratings Aleksandar Kolarov – 7 out of 10 Did little going forward but his main job was to deal with the threat of Messi, which is never easy. Manchester City vs Barcelona player ratings Fernandinho – 7 out of 10 Broke from midfield well to support the attack and barely stopped running. Manchester City vs Barcelona player ratings Raheem Sterling – 8 out of 10 City’s most dangerous player on the night. Should have scored just after half time but was a constant threat. Manchester City vs Barcelona player ratings Kevin De Bruyne – 8 out of 10 Pretty anonymous until his stunning free-kick gave City the lead and was a constant threat in the second 45 minutes. Manchester City vs Barcelona player ratings Ilkay Gündogan – 8 out of 10 Beautifully-timed run for both his two goals, arriving in the right place at the right time – something he is quickly making a habit of doing. Manchester City vs Barcelona player ratings David Silva – 8 out of 10 Passed through the lines well and won the free-kick cleverly for De Bruyne’s goal. Manchester City vs Barcelona player ratings Sergio Agüero – 8 out of 10 Why didn’t he start at the Nou Camp? Aguero was exceptional as always and never gave Barca a moment to rest. Manchester City vs Barcelona player ratings Marc-Andre ter Stegen – 6 out of 10 His range of passing was inch perfect throughout but could be blamed for his positioning on De Bruyne’s free kick. Manchester City vs Barcelona player ratings Sergi Roberto – 4 out of 10 Played a blind pass to allow City to equalise and almost repeated the mistake in the second half. Manchester City vs Barcelona player ratings Javier Mascherano – 5 out of 10 Was stretched by City’s brilliant attack throughout the entirety of the second half. Getty Images Manchester City vs Barcelona player ratings Samuel Umtiti – 5 out of 10 Was lucky not to give away a penalty in the first half as Sterling was booked for diving instead. Manchester City vs Barcelona player ratings Lucas Digne – 5 out of 10 Was given a bit of a run around by Sterling but supported Neymar well when attacking. Manchester City vs Barcelona player ratings Ivan Rakitic – 5 out of 10 His metronomic passing was a little awry but a nuisance in his defending as he hustled City’s midfielders. Manchester City vs Barcelona player ratings Sergio Busquets – 5 out of 10 Struggled to stem City’s attack when they broke and was taken on too easily by Aguero at times. Manchester City vs Barcelona player ratings André Gomes – 5 out of 10 Replaced the injured Iniesta and missed a fantastic chance to equalise when he thumped the ball against the bar. Manchester City vs Barcelona player ratings Lionel Messi – 7 out of 10 His work for the opening goal was genius as he started and finished a sublime counter attack. Manchester City vs Barcelona player ratings Luis Suárez – 6 out of 10 Had a number of chances throughout and should have found the net with at least one of them. Manchester City vs Barcelona player ratings Neymar – 5 out of 10 Did really well for the opening goal but faded as the game went on.

“With Luis [Suarez] maybe now we are a bit more aggressive when we attack at speed, whilst with Pep we used counter-attacks less,” Lionel Messi said earlier this week. His goal was a metaphor for that: a counter-attack of maybe 20 seconds’ duration, which Messi began by blocking a shot in his own penalty area, before running the length of the pitch to take back from Neymar and score.

From Barcelona, the metronomic, almost cloying, passing – the ‘carousel’ as Sir Alex Ferguson called if after Guardiola’s players had passed Manchester United to death in the 2009 Champions League Cup final – has gone. But it is not needed with trident of forwards. ‘Nearly unstoppable’, Guardiola had called the two wide members of that triumvirate – Neymar and Messi. When Nicolas Otamendi surrendered cheap possession, Neymar was bearing down on Willy Caballero like a guided missile. It took a very fine save to palm his shot away.

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This slip was part of a broader problem, as City’s attempts to match the Spaniards’ pace bred errors. That same pace initially made City’s forwards look almost sluggish by comparison. Aguero had a chance wide right to supply a cross two minutes after Barcelona led and took what seemed an eternity to deliver the cross which hit the first obstacle in its path, Samuel Umtiti.

But City were not ready to drop into another abyss and Guardiola’s demands are the reason for that. Aguero has been reduced to life on the edge here, recalled on Tuesday night but knowing that his place is no longer a God-given right. He had a point to prove and made it, having a say in all three goals, if the pass which drew the foul and decisive free-lick is included.

Guardiola recorded a famous victory against his former side (Getty)

Guardiola may feel the Argentine has more to offer. He has said he wants Aguero to be a greater presence in the six-yard box, raining shots on goal, and here he was principally a provider, operating deep. In the second half, though, Enrique’s players could not come close to him. Nor to David Silva, the mercurial talent whose movements and instincts were sharper and more unpredictable than any other player on the pitch. By the end they were rocked back on their heels, desperately trying to stem the attacking movements to which Raheem Sterling and De Bruyne added.