City lost 1-0 to Borussia Dortmund and finish the group stage bottom, without a victory and just three points in total.
“You can’t be embarrassed when you play 100%,” said Mancini, whose side have scored just four times in the past five games.
“I don’t feel we lost our application but if you want to win games you have to score and at the moment we have this big problem. When we have a chance we don’t convert it and we need to resolve this.”
