The City manager’s decision to leave out Sergio Aguero backfired while Claudio Bravo, the goalkeeper in whom he has invested much trust, was also sent off in a Champions League mauling at the Nou Camp.
Lionel Messi took full advantage to help himself to a hat-trick while Neymar, who also missed a penalty, added the fourth goal late on.
Asked if the defeat was his worst in football, Guardiola said:
“No, that was against Real Madrid for Bayern Munich, because in that moment I didn’t make the correct decisions.
“We lost the game 4-0, yes, but we are a new club, we are getting to know each other. We are a club that for 35 years was not in Europe.
“We came here and played with huge personality but it is always difficult to play Barcelona with 11. With 10 the game was over. Until then the game was open.”
On Aguero’s omission, the former Barcelona boss said: “It was my idea. I wanted one more midfield player in that position and that was the reason why. I spoke with him and he was good.”
City were trailing only 1-0 when Bravo blundered attempting to play out from the back, gifting the ball to Luis Suarez. The keeper was suddenly stranded outside his area and he handled deliberately attempting to block Suarez’s attempted lob.
“There will be no change. It stays the same.
“Football is a game of mistakes. Of course he knows what he did, but he has a lot of experience and he’s one of best goalkeepers in last 10 years, so I don’t have doubts about him.
“It is a mistake but some things happen. He is the first one to be disappointed with what happened but it is football. He will learn.
“But I’m sorry, until the last day of my career as a coach I will try to play from our goalkeeper.
“Sometimes there are mistakes and sometimes you have to kick the ball out but most of the time, when we play good, it starts from there.”
Guardiola found positives in the performance.
He said: “The last time I came here we controlled but we didn’t create. Today we created enough and we arrived at the byline many times. We created enough chances to score one or two goals.
“But we know Barcelona, with their strikers, when they arrive they punish you.”