Patrick Kluivert's fifth minute goal secured victory and a semi-final place for the home side despite a sustained assault on their goal for much of the 90 minutes.
"We started a little bit shaky and conceded a goal, which I am disappointed with," said the skipper, reflecting on a lost challenge with Alan Shearer that allowed the striker to set up Kluivert. "I've gone in, I thought Shearer was going to go in as well and it has kind of ricocheted into his path and we were punished from there.
"After that we bossed the game really and I think it was a game where if we had scored one we would have gone on and won it. After playing so well we are so disappointed to have got nothing from the game.
"It was a good performance by us, we had a lot of young players out there and Newcastle have got some experienced players. We dominated the game and that is not easy to do here - but they have won it."
Taking heart or positives from the manner of performance was not really at the forefront of the England international's thinking, but he knows any lingering disappointment must be shaken off ahead of the Charlton game on Wednesday.
"It's good to know we did everything we could, but we haven't won the game. That is the main thing - we want to be winners. We could take heart from the performance but it would have been nicer to have played badly and won.
"Charlton are in a similar position to us in the league and it is a real tough game. It will be an important three points and we've got to make sure it is us that gets them on Wednesday.
"That is what we do have to take into the next game, the fact that we have played well and if we play like that against Charlton I am sure we will get the points."
The fact that the team played well was of little consolation to Ledley King after narrowly and unluckily losing out to Newcastle in the FA Cup quarter final at St James Park.