Newcastle United boss Steve Bruce said there was “a complete surrender” from his side as they were hammered 5-0 by Leicester City.
The Magpies, who had Isaac Hayden sent off with the score at 1-0, are second from bottom in the Premier League.
“Effort is a big, big part of the game and we have not done enough,” Bruce told BBC Sport.
“The nitty gritty is we have not laid a glove on Leicester in the second half and the white flag came out too early.”
Newcastle went into the break one goal down, following Ricardo Pereira’s opener, but were reduced to 10 men after Isaac Hayden’s dangerous tackle on Dennis Praet.
The visitors crumbled in the second half, conceding three goals in a 10-minute period before Wilfred Ndidi’s 90th-minute strike completed the five-goal rout.
It was Bruce’s joint-biggest defeat as a manager in the Premier League and a fourth league loss of the season.
Bruce, who took over at St James’ Park in the summer after the departure of Rafael Benitez, said his side were “nowhere near good enough” in a game where they failed to register a shot on target and had just 31% of the possession.
“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 said.
“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.”