Manchester United manager Erik ten Hag says he has belief in his players and that they are determined to “put right” their poor form.
The defeat came amid a disappointing start to the Premier League season, with the Old Trafford club in eighth place with 15 points from 10 games.
“They want to put this right,” Ten Hag said of his squad.
“We know the standards here and we have to make those standards every day.
“We will fight back. The players are strong, the coaches are strong and the manager is strong.”
United were also comfortably beaten 3-0 by rivals Manchester City prior to the Newcastle defeat, and visit Fulham on Saturday (12:30 GMT).
Questions have been asked about the togetherness of the squad, but Ten Hag dismissed those as he highlighted a 2-1 win against Brentford on 7 October when two Scott McTominay goals in added time secured victory.
“Remember only the fight we showed against Brentford and the comeback. If there wasn’t spirit or fight in the dressing room, we couldn’t do that,” said the Dutchman.
Ten Hag will be without midfielder Casemiro for several weeks because of a hamstring injury suffered against Newcastle.
A United statement said the 31-year-old Brazilian “was withdrawn at half-time due to the issue, and subsequent assessment has revealed a strain that will keep him out for a number of weeks”.
Casemiro joins defenders Lisandro Martinez, Luke Shaw and Tyrell Malacia on the sidelines, while centre-back Victor Lindelof could be out for the Fulham game.
Central defender Raphael Varane, who has also had a spell on the sidelines this season, is available against the Cottagers after missing the Newcastle cup tie with illness.
“The intention is clear but the execution isn’t,” said Ten Hag about his side’s lack of identity.
“At the moment we are in with so many changes in each game. We can’t line up the same for two or three games, and last season was the same.
“Now, often we miss players in the back four and we have to adjust, also in the midfield. We are missing Casemiro.
“We have to win and I don’t want to find excuses if we don’t win.”
He added: “I have a good squad and I’m convinced in the players in this dressing room.
“These players, as you saw last year, can do better and I need to let them play better. That is my responsibility.
“I’m not thinking about [transfer] windows because I have a good squad and we will play better when players return from injury.”
Ratcliffe willing to spend on Old Trafford improvement
Simon Stone, BBC Sport
Prospective United co-owner Sir Jim Ratcliffe is willing to commit millions immediately for stadium infrastructure improvements if a planned deal to buy into the club is approved.
The search for “strategic alternatives” for United, launched by the Glazer family almost 12 months ago, is still to be completed – despite a widely held belief that Ratcliffe’s Ineos Group is going to secure a 25% stake.
Numerous sources close to United have told BBC Sport the process needs to be speeded up in order to allow clarity over Ten Hag’s position as currently, Ratcliffe cannot be consulted over the Dutchman’s future.
It is thought Ratcliffe will pay around £1.25bn to buy a quarter of the club but many fans, uneasy at the prospect of the Glazers remaining in control, have questioned where the money will go and if any of it will be used to make badly needed improvements to Old Trafford.
However, it has now become apparent that in addition to paying for that 25% stake in United, Ratcliffe would provide an additional sum, that would not be added to the club’s current debt, for urgent work on the stadium.
It is accepted the sums involved would not cover all the work needed, which some have estimated will cost £1bn, but it is seen as a sign of Ratcliffe’s intentions for United.