The Magpies were beaten for the third consecutive time by their local rivals as they went down 3-0 at St James' Park in the Premier League.
"It's so disappointing and of course it hurts. Everything went wrong. You cannot put your finger on one thing because it was everything," he told The Sun.
"We need to show the fans we're up for the challenge. We have to stay focused and although we are going to get a lot of criticism, we just have to deal with it."
Newcastle continue their Premier League campaign on Saturday when they face Chelsea at Stamford Bridge.