The Blaugrana boss felt his side were not always completely dominant in the first leg against Manchester City but put in the desired performance after the break to claim a 2-0 win
The Blaugrana became just the third team to beat Manuel Pellegrini's men on home soil this term as goals from Lionel Messi and Dani Alves secured a 2-0 win.
And the Argentine got the result he was after but admitted that Barca had lost control of the match for a period in the first half.
"For 10 minutes during the first half we lost control a little but in the rest of the game we did well," the Argentine coach told reporters.
"We came here to win. There was no moment when we thought in any other result that wasn't winning. I think the result is fair.
"We have to remain calm and continue along the same path because there is no time to relax as we must now start thinking about our next game in La Liga.
"I don't have the assurance that we're in the next round, but I do have the tranquility of doing a good job away from home.
"We won the first 90 minutes in a match that lasts 180. We’re going to approach the second leg as if it were 0-0.
"We have clear objectives in each tournament. We can play better or we can play worse than tonight but in no way are we going to relax."
Barcelona are back in action on Sunday in a visit to Real Sociedad as they look to retain their place at the top of La Liga.