The Spaniard is certain his side can overturn their 2-0 first-leg deficit against AC Milan at Camp Nou on Tuesday and called for supporters to help their team
The Rossoneri hold a commanding advantage going into the return fixture on Tuesday, but the former Manchester United defender is adamant his side have what it takes to progress.
"Any fan who doesn't think we can turn it round against Milan should give his ticket for the game to someone who does," the defender told reporters at the pre-match press conference.
"I ask the fans to look at the last 10 or 15 seasons. People have a short memory and they need to know that this team can win tomorrow and can do a lot, lot more.
"We need 90,000 people to believe in us and believe we can qualify for the quarter-finals."
Meanwhile, stand-in coach Jordi Roura has called for focus ahead of the tie, having been planning for the fixture for the last few days.
"The perfect match is always the one that ends well and takes us to the quarter-finals," the 45-year-old added.
"This match lasts 90 minutes so we have to keep our head on our shoulders, keep our cool and not lose control of the game.
"We have been planning for this match for days, but we have today's training session to finish before deciding on the starting XI. I still have a few doubts in my mind about who will play."
Barcelona and Milan kick off at 20:45CET on Tuesday.