Daniel Farke felt his side didn't make the most of their early control after seeing them go down to a 2-1 Sky Bet Championship defeat at Bolton on Saturday.
The Canaries dictated the opening stages, but were rocked as goals from Gary Madine and Adam Armstrong left them two behind at the break.
Josh Murphy pulled one back for the visitors deep into injury-time, but it proved to serve only as a consolation as City's excellent away run came to an end.
"You couldn't see this result coming in the first 30 minutes. We had the game totally under control.
"It was just a question of time before we scored but Bolton were effective while we weren't. We weren't perfect in our defending and missed a lot of chances.
"We scored in the last minute but it was too late to turn the game around. We had the game totally under control and because of that it's very frustrating."
Highlighting his team's profligacy as they spurned decent chances in the opening period, the Head Coach added: "At the moment, we have to defend perfectly to win games.
"We are scoring too few goals. It's been the story this season. Cam [Jerome] knows he had good chances.
"Today, he wasn't able to use them and he's pretty annoyed. I was a striker too and sometimes you have difficult times.
"Ten days ago we were team of the moment but now we have to turn things around after the international break."