Barcelona boss Luis Enrique said he has "no explanation" for Tuesday's Champions League defeat to Manchester City.
Enrique watched his team throw away a lead to lose 3-1 at the Etihad Stadium and told Spanish media he did not know why. Per Mike Keegan of the Daily Mail, Enrique said: "I have not got an explanation. There is no explanation.
"I think it's been one of the best 40 minutes we have played, particularly on a stage like this against a top-quality rival. In the second half we hoped to continue to dominate but it couldn't be. That's because of errors and pressure from the opponent."
Enrique added: "City took advantage of our errors, and they have some great players. The first 40 for us, the following 50 for them. The result reflects that. They played very well. They were aggressive and provoked more errors from us than we did from them."
Barcelona took an early lead through Lionel Messi, but City responded in fine fashion to claim a famous win.
City's victory was their first over the Spanish side in Europe after five previous failed attempts, and, as noted by Chris Bevan of BBC Sport, manager Pep Guardiola said he believed the result can inspire the club.
Now they will realise that they have beaten the best team. Future generations will see that and know they have to do that again. That is a process. It was the same with the group of players with Joe Hart and Vincent Kompany who won the title twice in five or six years together. The players arriving at the club now understand they have to do that, or try to do that too.
Certainly Enrique would have been surprised by the turnaround in City's performance, particularly after winning the first encounter so comfortably, 4-0, and looking largely in control before going a goal up in Manchester.
The intensity City showed was the key to success and will give Guardiola confidence, if he needed it, that his methods are beginning to have an impact.
A poor run of results had seen City go six matches without a win, a surprising slide considering they opened the campaign with 10 wins on the trot.
As James Ducker of the Telegragh noted:
It was hard to recall Barcelona being beaten at their own game in quite such a brutal way, battered into submission over the course of a second half when City came of age in the Champions League, bewildering their illustrious opponents with the intensity and dynamism of their high press.
The change in fortunes that had Enrique scratching his head was spearheaded by City enforcer Fernandinho, who gained the upperhand in midfield before injury forced him off on the hour mark.
The Brazilian has flourished under the new regime and his midfield steel, allied to his passing ability, has seen him become a central figure in the Guardiola revolution.
Two-goal Ilkay Gundogan tweeted this picture of the City celebrations:
City's display in coming back to beat their nemesis could act as the catalyst to kick-start their campaign. Despite being top of the Premier League, signs were creeping in that all was not well as the club adapted to a new playing style.
Guardiola will also be boosted by Gundogan's goalscoring form, following up a league double against Southampton with another brace against Barcelona.
However, his presence so far this term appears to have given City an extra dimension alongside Kevin De Bruyne, Raheem Sterling and Sergio Aguero.
For Barcelona manager Enrique however it may be a case of back to the drawing board after City stripped the Spaniards of their dominant aura over them.
If City now progress out of Group C and go deeper into the Champions League, Enrique will need to devise a plan to overcome a revitalised outfit should the two sides face up to each again.