Barcelona head coach Luis Enrique acknowledged Manchester City's errors were the reason for his team coasting to a 4-0 Champions League victory at Camp Nou.
Lionel Messi, back in the starting line-up following a groin injury, capitalised on a slip from Fernandhino to put the hosts in front but the Group C encounter was an evenly contested affair until ex-Barca goalkeeper Claudio Bravo was sent off after 53 minutes.
Bravo's botched clearance and subsequent handling of Luis Suarez's goal-bound shot left referee Milorad Mazic with little choice and Messi clipped home from the edge of the area in the 61st minute before a further mistake from Ilkay Gundogan allowed him to complete his hat-trick.
Neymar had a penalty saved by Willy Caballero but responded to round off the scoring and a humiliating return to Catalonia for City boss Pep Guardiola.
"There have been serious errors [from City] in the game and that is always a plus," Luis Enrique told a post-match news conference. "Taking advantage of those mistakes is key and we've taken advantage of them.
"This is a game of errors. It has not been easy because of the quality and positioning of the City players is there.
"The golden ages of [Barcelona] have come when they have balanced defensive and offensive sections to be effective.
"And then there is Messi, who plays as if he were in the backyard."
An occasionally testing evening for a Barcelona defence featuring Javier Mascherano out of position at right-back was compounded by first-half injuries to Jordi Alba and Gerard Pique, while the latter's replacement – Jeremy Mathieu – was sent off with 15 minutes to play.
"The success of a team's defensive level is a matter of all players," Luis Enrique said.
"If we had not played collectively the outcome would have been different."