Sections of the Spanish media claimed that the two close friends had clashed in the tunnel – but Aguero played everything down.
He admitted to the Spanish media that he had heard Messi say “something”, but dismissed any hint of a spat between the two Argentinian international team-mates.
Aguero said: “It was nothing serious. I heard something, but I don’t know what happened.
“I thought Messi said something to me, but he didn’t, and then we talked about other stuff.”
But he told a different TV broadcaster: “We haven’t talked. Whenever you lose, you’re not very happy.
“I saw him there, he was feeling bad. I know him well enough to know when he’s bad, when he’s good. But when you lose, nobody’s good!
“When one loses, you have to respect them. Leo wasn’t in the mood to talk and I respect that.”
Aguero also dismissed Barcelona claims that he had handled the ball just ahead of Ilkay Gundogan’s killer third goal.
Jesus Navas crossed from the right and the ball struck Aguero on the arm before falling perfectly for the German to score his second of the match.
He added: “I thought that Ter Stegen would touch it and, because of that, it went past me a bit, but I had my hand by my side and there was no intention to use my hand.
“It’s normal that they complain, but luckily we were 2-1 up already and that goal calmed us.”