Steve Bruce admitted he was disappointed with the lack of effort from his players during the 5-0 loss to Leicester on Sunday.
The Magpies had already fallen a goal behind when Isaac Hayden got himself sent off for a dangerous tackle on Dennis Praet, with two strikes from Jamie Vardy, Paul Dummett's own goal and Wilfred Ndidi's late effort complimenting Ricardo Pereira's earlier goal.
Speaking to BBC Sport after the game, Bruce admitted his side surrendered far too soon as the Foxes ran riot at the King Power Stadium.
He said: "Effort is a big, big part of the game and we have not done enough.
"The nitty gritty is we have not laid a glove on Leicester in the second half and the white flag came out too early.
"We have to apply ourselves better than what I've just witnessed there because it was a complete surrender too quickly and too easily," he added.
"Too many felt sorry for themselves, yes, we made mistakes and we got badly punished but to react in that way was the disappointment for myself, the players and the travelling support, which was quite unbelievable.
"Being a manager or coach, I ultimately accept the responsibility because it's as bad an afternoon as I can remember.
"I have heard lots of nonsense about tactics but the big thing is about showing pride and having a go. We have let everybody down today.
"I always knew it was a challenge, I was delighted to take the challenge but let us hope we can turn it around. I have the appetite to do that."