City were hammered 4-0 on Saturday, marking a fifth consecutive defeat for the champions.
Walker later said, "It's hard to stand here and speak about it when I haven't properly digested it yet. I've stood here when we won titles so I'll stand here for defeats too.
"This is the most frustrating thing as a defender. I don't care about scoring goals, I'm bothered about clean sheets and we're not doing that. You have to go back to the basics and get a clean sheet. If we concede four goals at home we have to score five.
"It's not just the back four, five or six - it's all 11 players on the pitch.
"I wouldn't say we've lost confidence together. I've spent eight years with this group. You lose confidence as a team but we have to remember what we've achieved together. What we've achieved in the past means nothing, it's history. We have one team above us doing really well. We'll keep fighting to the end as we always do. The best way to turn this round is on Tuesday. Hopefully the mojo comes back and we see the normal City from the past eight seasons.
"Your powers don't just go. We know our qualities and weaknesses. You get a win, you get your confidence and we're back to how we used to feel."
On next Sunday's game at Liverpool, Walker added: "It's a great game to turn it around and take three points from the team who sit above you. But we can't put in a performnace like that or we'll get walked over. We have a Champions League game to prepare for that massive game on Sunday and keep within touching distance of Liverpool."