Roberto Mancini believes City must shore up at the back in order to progress through to the knock-out stages of the Champions League.
The Blues let a 2-1 lead slip in the final moments of an exhilarating game against Real Madrid and ended up losing 3-2 thanks to some slack defending around the box.
“We didn’t defend as we can on the edge of the box and made some mistakes – we cannot continue to defend this way and we need to resolve this problem quickly,” said the City boss.
“We played too deep and this invited problems. Madrid were better than us in the first half but we improved a lot after the break. We are disappointed because we were 2-1 up with five minutes to go and if you find yourself in this situation away to Real Madrid, you should pay more attention and go on and win.
“Teams can lose here, that is not a surprise but we have lost from a good position – that is the disappointment, but I was happy with our performance in the second half.”
Mancini refused to blame the fact this is only City’s second Champions League campaign, adding: “We can’t continue to talk about experience because we have good players who are used to playing in big games like this.
“Other teams will lose here, too, but now we have five games left and it is important that we beat Borussia Dortmund in our next game. That won’t be easy because they are another top team.
“It will be difficult and we know ever match will be hard, but we should go through to the group stages this year.”
Joe Hart, who made several stunning saves during the game, said: "It's not on. You can't go 2-1 up and lose the game. We can only blame ourselves.
"They are a very good team and so are we. We dug deep, got a lead twice and threw it away. It's hard to come off the field after losing 3-2 and be positive."