Messi scored a fabulous hat-trick as Guardiola was given a harsh lesson in facing the brilliant magician with a Premier League side as Manchester City were beaten 4-0 by Barcelona.
Messi has now scored 16 goals in his last 15 games against English sides and the worrying thing for Guardiola is that he only looked half-fit after recovering from a three-week injury lay-off. He will be even fresher in the return tie at the Etihad in two weeks’ time.
Then City will be without former Barca keeper Claudio Bravo, who picked up a ridiculous red card and all-but ended their hopes of snatching a result last night.
Barca were already ahead through Messi when Bravo fluffed a 56th minute clearance straight to Luis Suarez and stopped his goal bound lob with his fingers. Barca punished City horribly adding thee more goals as their shortcomings were exposed and it could have been worse had defender Jeremy Mathieu not also seen red.
Bravo’s mistake was disastrous and makes Guardiola’s decision to force out England No. 1 Joe Hart in favour of a sweeper-keeper look questionable.
“I spoke with him, he was disappointed but it’s part of the game,” Guardiola said of Bravo’s dismissal.
“At that level it is hard, but until 10 against 11 it was open and we were competing against a team with a big personality. But after the card it was over. But every game since Celtic has been the same, against Everton it was the same with an own goal and two missed penalties. We need to change the atmosphere.
“We were there, we were in the game. We were pressing, we had the possession and we made the chances. We did it but we didn’t take the chances and you have to do that to win the game
“We knew from the beginning it would be a tough group, now we have to focus on Southampton.”
However, had he signed Barca’s other keeper Marc-Andre ter Stegen, the result may not have turned out the same way. Guardiola had admitted before the game that he had been interested in the German international and Ter Stegen made a few fine saves when the game was in the balance and belied his current run of poor form.
Even substitute Willy Cabellero showed Bravo the way to do it with a late penalty save from Neymar, although Messi had scored twice by then, and the Brazilian finally beat him in the last minute.
The inquest will begin immediately for Guardiola, who had caused a huge selection surprise before kick-off when he left striker Sergio Aguero on the bench.
The Argentine, who has two hat-tricks already this season in the Champions League, was expected to start having been left on the bench for City’s 1-1 draw with Everton at the weekend.
But the City boss confirmed before kick-off that is was a tactical decision - rather than a recent adductor injury he played through on international duty last week - with the Catalan knowing exactly the dangers of his former employers.
He opted to pick Kevin de Bruyne up front to try to create a congested midfield and frustrate Barca’s ball domination and it seemed to be working well in the opening exchanges.
Ter Stegen and Gerard Pique saw plenty of the ball in their own area as City pushed them back in a confident opening.
But it all changed in the 18th minute when Messi punished a slip by Fernadinho in his own box to give the home side the lead.
The Brazilian looked ready to clear the loose ball in the box when he lost his footing and Messi pounced - taking the ball around Bravo and burying the ball in the back of the net.
It knocked City out of their stride and they conceded territory as the attacking three of Messi, Neymar and Suarez interchanged neatly and got behind City’s back four.
But after losing Jordi Alba to an early injury, Pique then hurt himself and City created two good chances before the Spaniard was taken off.
First Nolito drilled a low shot that was comfortably kept out by Ter Stegen before Ilkay Gundogan danced through the home defence only to see his strike kept out by the arm of his Germany teammate.
Defender John Stones then missed the best chance of the first half when he was left unmarked at the back post but could only plant a header from David Silva’s free-kick off-target.
Losing both Pique and Alba, particularly, was a big loss for and Raheem Sterling grew in confidence as he targeted Lucas Digne, beating him on a couple of winding runs but failing to pick out a player in the box.
But just as they causing more problems at the start of the second half, Bravo saw red for a crazy individual error.
He made a hash of a clearance - gifting the ball to Suarez and having to stop his shot with his fingers.
Caballero came on and was beaten two minutes later - Messi stepping inside and unleasing a low drive that beat him at his near post.
Barca were 3-0 up shortly after when Gundogan tried to find Stones but Suarez raced clear and passed to Messi to complete his hat-trick.
Messi was then brought down by Aleksander Kolarov in the box but passed up the opportunity to add a fourth with Neymar taking the spot-kick. But his poor penalty was comfortably saved although the Brazilan added a late fourth to compound City and Guardiola’s misery.
Ter Stegen 7, Pique 6 (Mathieu 4, 39), Mascherano 6, Umtiti 7, Alba 5 (Digne 8, 6), Rakitic 7, Sergio 6, Iniesta 8 (Gomes 79, 5), Messi 9, Suarez 8, Neymar 7.
Bravo 5, Zabaleta 6 (Clichy 53, 6), Otamendi 7, Stones 6, Kolarov 6, Fernandinho 7, Gundogan 6 (Aguero 79, 5), Silva 7, Sterling 7, Nolito 6 (Caballero 53, 6), De Bruyne 7.