The result leaves City 14 points behind leaders Liverpool.
Walker remarked afterwards, "Us as defenders need to hold our hands up. We need to keep clean sheets and strikers maybe need to put more away.They had a game plan and it worked. They have quick players in quick areas and they are going to hurt you on the counter. Credit where credit is due, they stepped up today. Fair play.
"Can't fault the manager. He has won numerous trophies. I can't put my finger on it. It is going to be difficult, Liverpool are on fire. They are getting wins and we are not. It is a big gap but we will fight until the end."