The Magpies recorded their first victory at Old Trafford in 41 years on Saturday and moved up to seventh in the table, within three points of a Champions League place.
Alan Pardew's men have now claimed five wins from six games - including victories against Chelsea and Tottenham - and Krul feels there is still more to come.
"I have always said we are a top team," said the Dutch keeper.
"We have everything we need to succeed, in addition to a fantastic fanbase.
"Unfortunately, over the years, the results haven't been there.
"This year we have a great squad and the fact we are not in the Europa League is a big factor in our favour.
"Things are looking really good at our place."
Yohan Cabaye netted the winner against the champions after 61 minutes, firing home from a Moussa Sissoko cross.
Newcastle had earlier had a lucky escape when Patrice Evra headed against the post and the ball rebounded onto Vurnon Anita's arm, but referee Andre Marriner did not award a penalty.
"It was a truly deserved victory," said Krul.
"We went to Old Trafford with a lot of confidence because have had some great results over the last few weeks. We also knew they had had some bad results at home.
"We felt if we came out fighting we knew we would have a chance.
"They had a couple of shots but they weren't as threatening as normal and we just capitalised on it massively."
Newcastle went into the game at Old Trafford on the back of a 3-0 midweek defeat at Swansea, and Krul admits their preparations for that game were far from ideal.
"It was a long journey to Swansea in the first place and then we had a long day in the hotel waiting for the game," he said.
"We were a bit sloppy in the first half and paid the price for it.
"We started this game with the same intensity as the games before that.
"When we do that, we can beat anybody."