Pep Guardiola felt Manchester City forgot to attack in the second half against Basel as his side suffered a first home defeat since December 2016.
Despite losing 2-1 in Wednesday's Champions League last-16 second leg, City progressed to the quarter-finals for the second time in the club's history thanks to a 5-2 aggregate victory.
Guardiola's men set a new passing record in the competition, but having made nine changes from the first leg City lacked invention and penetration at the Etihad Stadium.
And the Catalan was critical of a flat performance that saw the Premier League leaders slip to their second Champions League loss of the season – they suffered a 2-1 defeat in a group stage dead rubber away to Shakhtar Donetsk.
"From tomorrow we will be happy to be in the quarter-final for the second time at this club," Guardiola told a post-match news conference. "We are new in that position. We are so happy for that.
"The first half was quite good. The second half we forgot to attack. You must pass the ball to attack. To pass [just] to pass is nothing. The second half was really poor.
"It's not easy to play [with a 4-0 advantage]. We tried, we spoke about that. We created a lot of chances at 1-0 and we were good.
"After 1-1, the best way was to create with the build-up. We just passed for ourselves and that is not football.
"In the quarter-final it's not going to happen that we are going to play games at 4-0."
Guardiola handed a second Champions League start to 17-year-old midfielder Phil Foden, who featured alongside veteran Yaya Toure, 17 years his senior.
"It was good," the Catalan said of Foden's display. "In the second half, with Leroy [Sane], he was the only one who tried to be aggressive.
"It doesn't matter if you lose the ball. The other ones… just to pass the ball so we don't create a lot of chances to score a goal.
"Bernardo [Silva] and [Ilkay] Gundogan, maybe there were tired [from] a lot of games like at Wembley [in the EFL Cup final] and against Arsenal and Chelsea.
"For players like Yaya, Danilo, for John [Stones], for the other ones, it is good to have 90 minutes."
Gabriel Jesus played the full 90 minutes on his first start of 2018, giving City an eighth-minute lead as he continues to come back from a knee injury.
"He fought, he needs rhythm," Guardiola added. "When you are out for a long time you need the rhythm to come back. Of course, the goal will be good for his confidence.
"You will find all the clubs in the world when you make six or seven changes, always the team is not the same.
"That's why I insisted to start well and we did well in the first half. In the second half we just passed the ball to pass the ball. It was everything slowly, without rhythm."