Palace jumped to a 2-0 lead, before City fought back to eventually win 5-2 at the Etihad.
Afterwards, Glasner conceded: "Our defending was not good enough today.
"We made too many mistakes and gave a team like City so many chances.
"But I think we will learn from this game and we have to learn. The last time we conceded five was against Arsenal and the players did really well learning from that.
"We will analyse it, we will show them, we will train on it, and hopefully we will do it better the next time."
He added, "It was unusual for us to not put pressure on the ball. It was a clear pattern, we always protected the depths first.
"Twice we were surprised and then we got punished and it's difficult to come back. The start was great, how we played. In our first goal, we moved the ball from left to right, always knowing we had a two v one, on the opposite side.
"But the longer the game lasted, the less we could do it and that's why we lost the game."