The brilliant Argentinian struck a superb first half hat-trick to switch the balance of power in a tie Arsenal had momentarily threatened to win, before adding a fantastic fourth goal in the closing stages to seal a memorable night for Guardiola's side.
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And Guardiola, who recently claimed to be lost for words to describe the brilliance of his star player, chose to focus on the player's human aspect while all around were marvelling at the latest chapter in the consecration of a truly wonderful footballer.
"The good thing about Messi is that tomorrow he will get up and look for the affection of his people and his team-mates," he said.
"I like the love he has for football and his anonymous character," the Barca coach added.
For Messi, it was a satisfactory night, but there was no question of wild celebrations or believing the hype.
It was put to him that a similar performance would be handy on Saturday in the vital league match at Real Madrid. And Messi was as honest and as humble as ever.
He said: "I don't think so, we would be happy with any kind of win, a 1-0. We are happy to go through tonight, but we have to keep going."
Guardiola added: "Leo was brilliant and he was decisive."
But asked how he would describe the performance of a player who is still only 22, the Barca coach said words were insufficient.
"You have to see it - it is not something you can describe because you have to see it to believe it," he said.
The former Barcelona captain claimed the whole club deserved praise following another passage to the semi-finals of Europe's premier club competition.
"All the players were brilliant and I think it's a great achievement to be in the semi-finals again because this competition is so difficult," he said.
"I congratulate the team and beyond that, the club, because in five years we have played four Champions League semi-finals and that speaks highly of the club," he added.
Messi's brilliance aside, Guardiola believes the win over Arsenal was fully deserved.
"We had more possession than them, though the game was dangerous, but when we equalised we calmed down and we were very aggressive in defence," he said.