The Argentinian forward capped a breathtaking display with two goals as Barça overturned a 2-0 first-leg deficit to clinch a place in the last eight. Yet for all their dominance, the assistant coach Jordi Roura dismissed suggestions that his team are favourites to win the competition.
He also indicated that Tito Vilanova, off work recovering from cancer of the saliva gland, may return to his job soon, after Charly Rexach, who is adviser to the club's president, had revealed that he expected the first-team coach to be back in Barcelona on 25 March.
Roura praised his players for their intensity and admitted that there was a redemptive quality to this victory after a fortnight in which they have been subjected to what he described as "exaggerated" criticism.
"I have spoken to Tito and he is very, very happy at the result and the way we played," Roura said. "In theory, Tito will be back soon.
"We're happy, we're satisfied and we're still in the Champions League. Some of the criticism of the team was over the top. It was exaggerated. We were not so bad before. Tonight, Milan struggled to get into the game, especially in the first 20 minutes, but I would not talk about things that Milan did wrong; I would talk about the attitude of Barcelona, about how they pressured and worked.
"They made it look like Milan did things wrong but it was more that we did things right.
"If there is one thing that surprises me about the players, one thing I have learned, it is that they are so competitive despite having won it all. These are players who really feel it, who hurt when the team loses, and that is one of the reasons why they are so good. These have been hard times but they were extraordinary. They have a voracious appetite."
Roura singled out Messi for special praise after the forward scored the first two goals to put Barcelona on the right path.
"People speculated that Messi was not in a good moment, they said I-don't-know-what and I-don't-know-why, this and that. But if anyone had any doubts about Leo, they only have to look at tonight," Roura said.
"He gave another magisterial lesson in how to play football. He has shown once again that he is extraordinary and that on the big occasions, surrounded by great players, he can do amazing things."
Roura also praised David Villa for his contribution up front, adding: "We chose him because we knew that he could draw the attention of the central defenders away from other players and give us depth to the attack. We also know that he takes a very high percentage of his chances." He added: "We played really well but any mistake, any tiny thing, could have put us out. A different result was possible.
"But I knew that; I knew that we would suffer and that emotionally it would be tough, and even if we had gone out I would have said the same thing: that I was very proud of the team. They showed great character and professionalism."
Asked if Barcelona were now favourites for the tournament, Roura replied: "No, no, no. We have got through and people will speculate that we are favourites. What I can say is that when we get to the next round we will try to get through that one as well, just as we did here. But favourites? Not at all. It's not like that. Tomorrow we will train, everyone will be happy, but this doesn't change things. We have to keep working and try to win on Sunday, then the Sunday after that."
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