Manuel Pellegrini condemned his side for some "very, very bad" defending as Manchester City beat Viktoria Plzen 4-2 on Wednesday.
The City manager fielded a second-string back four against the Czech champions and, despite the victory, was left frustrated by the sloppiness of the performance.
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And although City took their goalscoring run at the Etihad Stadium to 41 goals in 10 games, Pellegrini said they should be able to go forward without allowing their opponents as many opportunities.
"We can attack and we can score four goals without giving so many chances that we did today in defending," he said. "One of the most important things to be an attacking team is to know how to defend well. Today we did very, very bad.
"I am satisfied because we won the game 4-2 but I think we didn’t play well, we didn’t play with the intensity and the pace."
Joleon Lescott and Micah Richards were given chances to impress in a new-look defence, alongside Martin Demichelis and Aleksandar Kolarov, but while Pellegrini was critical collectively, he refused to say which players disappointed him most.
"I am not talking about just Richards and Lescott, I am talking about the whole team," he added. "I think the whole team must know how to defend. We didn't have the intensity or the pace today to do it and I am not talking about individual players."
Joe Hart was recalled in goal and made several fine saves but Pellegrini was coy when asked whether the England international, who made his first appearance for the club in a month, will keep his place against Swansea on Sunday.
"Joe Hart played very well," he said. "I didn’t expect that he would have to work so much during the game because I think this is the match when the other team, including Champions League and Premier League, had the most chances to score.
"From tomorrow [Thursday], we will start thinking about who is the best 11 to start for the next game, from the goalkeeper to the other players."
Sergio Aguero was replaced at half-time after scoring City's opening goal but Pellegrini confirmed the striker is not injured and was only ever going to play 45 minutes.