The former goalkeeper thinks that the Citizens will provide a real test on Tuesday and criticised fans who take football so seriously that they become violent
The Premier League side - who have been in fine home form this season under Manuel Pellegrini - host the Catalans on Tuesday in the first leg before a return clash at Camp Nou in March.
The former Blaugrana goalkeeper thinks the reigning Spanish champions will be truly tested by Man City - though he says they have learned from last season's encounters with AC Milan, Paris Saint-Germain and their 7-0 aggregate humbling by Bayern Munich.
"These knockout games are complicated because after a while you have to get into competition and start worrying about the opponent," he is quoted by Marca as saying. "We'll have to work hard.
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Zubizarreta also condemned the mecherazo incident in which Real Madrid forward Cristiano Ronaldo was hit on the head with a lighter in the Atletico Madrid Copa del Rey clash, suggesting fans need to put football into perspective.
"We all have to remove the tension in the stadium, where it seems like every game is the end of the world," the Barca transfer chief added.