The Slovakian shot-stopper, who made some crucial saves to keep the scoreline respectable, admitted the performance was nowhere near what it should have been.
It was the Magpies' first defeat in over a month, but it became a reality check as the memories of Norwich City and Leicester City came flooding back.
United have the chance to respond but it doesn't get much tougher as champions Manchester City visit next, and Martin Dubravka is keen for a reaction.
He told NUFC TV: "We gave them so much space, especially the second goal.
"It was a great cross, but we gave them so much space.
"The little pass (referring to the first goal) was crucial because after that it was difficult to react.
"We had a wall there but no excuses - we should do better, in all of the moments."
Speaking about the second goal, he continued: "There were two players alone, we know we should do better."
Attentions turn to City
With Man City already having a job on their hands to chase league leaders Liverpool, they will arrive at St James' Park with plenty to play for.
However, Newcastle beat them in the same fixture last season, and there will have to be an improvement to do the same again as Dubravka knows.
"We have beaten other top sides as well so why not try to do the same thing?
"We have to start with the basics, it starts on the training field and if anybody needs to do extra then do it.
"It's going to be tough but you never know.
"Let's play with the same confidence that we did when we were successful," he said.