Messi and Dani Alves had given Barca a 2-0 first-leg advantage at the Etihad Stadium and the same duo were on target again in a 2-1 win over the Premier League side at Camp Nou in the last 16 return clash on Wednesday.
The Catalan giants have lost three of their last six La Liga games to slip to third in the table domestically, but they are still in the hunt for the treble after securing their place in the quarter-finals of Europe's premier club competition.
Vincent Kompany had equalised a minute from time for City after Pablo Zabaleta was sent off for showing dissent following referee Stephane Lannoy's failure to award a penalty.
"We knew we had to get a goal to calm ourselves down because of the potential they have," Messi said.
"In spite of their goal, I think that the tie was never in danger. We played well throughout and achieved our objective of getting through.
"After two very serious slip-ups in the league, in games where we didn't play well, today we saw the Barcelona that people expect to see and we defeated a very difficult rival."
