The Premier League champions welcome Luis Enrique’s side to the Etihad on Tuesday with their striker hitting form having scored three goals in his last two games.
Barcelona knocked City out of the tournament 4-1 on aggregate last season, with Aguero missing the first leg due to injury but Kompany is backing him to impress.
“Agüero could be our Messi for a day, although Messi is amazing every day, in every game: two, three goals!” he told Marca.
“Messi’s consistency is what makes him Messi, the same as Ronaldo.”
City have never reached the quarter-finals of the Champions League but Kompany says it is time his team made an impact in Europe’s top competition.
“We’re up against a Barcelona team who in theory are better than us and who we have to beat by being… better,” he added.
“We can’t just survive against them. We have to be better on the night. At some point, this club has to step up in Europe and beat the best.”
Barcelona head into the game on the back of a shock Liga defeat to Malaga, and Kompany has urged City to attack the Spanish side.
“We have to play our usual game,” he added. “That’s how we won two titles last season, and we have to bring our ‘A game’ against Barcelona, outdo ourselves. We won’t beat them by sitting back and waiting to see what happens.”