The Blaugrana beat Manuel Pellegrini's side 2-0 in Tuesday's Champions League clash and the Argentine feels his side sent out a warning to the rest of Europe with the victory
The Blaugrana claimed a 2-0 Champions League last-16 win in England to put themselves firmly in control of the tie ahead of the return leg at Camp Nou.
Gerardo Martino's men have been made to endure criticism this season but the Argentine believes they showed just what they were capable of against Manuel Pellegrini's side.
"The team stepped up, we played a great game," he is quoted as saying by the club's official website.
"The result is really good for us and we know that the second leg will be difficult. City are a team that always create goalscoring chances.
"We have to continue to play like this. You can never relax when you're a Barca player. The decisive moments of the season are here and we are going to continue to fight for it all."
Meanwhile, goalkeeper Victor Valdes is feeling positive about his side's progress in the competition despite a balanced first half in Tuesday's game.
"We have a good feeling about this, especially because of how we played and how we pressured them," he said.
"Barca are always a rival that you have to think about. There's a lot of talk about how we lack the pressure we had in years past.
"We know that in a Champions League match you always have to suffer through at least 20 minutes of play."