Match report. Barcelona4 Manchester City0
Much of the talk had been about Lionel Messi before the match; all the talk was about Messi after the match; and the focus was almost entirely on him during the match. He produced another mesmerising display, scoring his seventh Champions League hat-trick and another reminder that he is the world's best player.
Of course Manchester City want him. Everyone wants him. City have Pep Guardiola but Barcelona have Messi. And this was another night belonging to him even if he was aided by some appalling City defending - gifting all three goals, in fact - and a terrible return to the Nou Camp for goalkeeper Claudio Bravo who was sent off.
It was a bad night for Guardiola, who was also returning to his former club. City have now gone four matches without a win and although this was the steepest of tasks - they have played Barcelona five times and lost on each occasion - they were still taught a lesson, with Neymar missing a penalty but adding a fourth goal.
It was also the story of two Argentine strikers. Guardiola had said before the game that he might do something courageous. He has also hinted, more than once, recently that Sergio Aguero needs to work harder. But the decision to bench the Premier League's best striker still came as a shock. Instead Guardiola played Kevin De Bruyne as a 'false nine', the role Guardiola moved Messi into with such spectacular success at Barcelona seven years ago.
The coach's intention was clearly to flood the midfield and deny Barcelona that relentless possession that he was so evangelical about while at the club because of its ability to wears down opponents. So we had the unusual sight of Messi hoofing the ball down the line as City applied the pressure.
With De Bruyne was furthest forward, and Nolito and Raheem Sterling in support, City made the brighter start, pushing deep into Barcelona's attack while walking the tightrope of leaving themselves vulnerable to the rapid counter-attack of Messi, Luis Suarez and Neymar.
The rope snapped. Or rather Fernandinho slipped, allowing, who else, but Messi to score. It came as Barcelona broke, with Messi collecting possession after Javier Mascherano was tackled. The Argentine pushed the ball into the feet of Andres Iniesta, who was running away from the City goal, across the face of the penalty area, but managed to flick the ball inside.
Fernandinho would have got there but fell over and opened the way for Messi to round goalkeeper Claudio Bravo and walk the ball into the net. It was cruel on City - who then almost gifted Barcelona a second as they allowed Suarez to shoot from a tight angle only for him to strike the side-netting - and it was 10 goals in his last eight Champions League ties for Messi.
Guardiola puffed out his cheeks, hitched up his trousers. He had seen that calm genius so many times before from Messi not least on his previous return to the Nou Camp two years ago, when his Bayern Munich team also took the game to Barcelona and were also undone by the Argentine, who famously dumped Jerome Boateng on his backside to score. On that occasion, it took him deep into the second half to struck. Here City were up against it with less than a quarter of the match gone.
They were rattled. Tackles became rash; the ball was quickly turned over and Messi delivered a free-kick on to the head of Ivan Rakitic only for him to steer the ball.
Finally City fashioned something with Ilkay Gundogan ferreting the ball through to David Silva who found Nolito and his Marc-Andre ter Stegen turned his low shot away with his legs. From the corner, the goalkeeper was forced into a far more spectacular save as Gundogan skilfully drove into the area, arced the ball goalwards and the keeper pushed away at full stretch.
Barcelona had to ring the changes as they lost two players to injury making their defence appear even more makeshift - they switched to a back-four that included three Frenchmen, none of whom start for France. Surely that would give City even greater hope?Certainly they should have been level. Silva's free-kick ran through to the far post where John Stones powered his header wide.
Immediately they could have been two-down as Messi worked his magic and found Suarez, whose shot was blocked by Bravo with an outstretched boot. The goalkeeper smothered the rebound.
Even after that, and still before half-time, City could have had a penalty when Sterling's cross struck Lucas Digne's hand but the referee was unmoved. De Bruyne struck the side-netting.
City appeared very much in this tie but then suffered a desperate blow.
Bravo rushed from goal and attempted to steer the ball to Stones, rather than simply clearing it, but sent it straight to Suarez who tried to lift it back over the goalkeeper.
Bravo instinctively stuck out an arm to block the ball even though he was outside the area, and was shown a red card. Barcelona fans chanted "Bravo" as their former player trudged off.
But it was over. Messi scored again. Once more City were undone by a mistake as the ball was easily lost, this time by De Bruyne, and again Andres Iniesta found Messi whose quick feet did the rest as he swept a low shot past Bravo's replacement, Willy Caballero, from the edge of the area.
Ter Stegen thwarted De Bruyne but it did not matter. Messi struck again.
And once more it was from an error with Gundogan's poor pass running straight to Suarez inside the City area who simply squared for Messi to turn the ball home. Barcelona were then reduced to 10 men themselves with substitute Jeremy Mathieu sent off after quickly collecting two yellow cards. Messi worked his way through again, was tripped by Aleksandar Kolarov, and allowed Neymar to take the penalty. Caballero saved. But Neymar made amends as he danced through and forced a shot beyond the goalkeeper to complete the rout.