Rafa Benitez's side find themselves in the bottom three and have lost three of their last four league games, scoring just two goals during that run.
But perhaps there is some reason for optimism after their spirited performance in the 2-1 loss at Chelsea. Benitez's men were undone by two superb goals from the home side, and did cause Maurizio Sarri's side plenty of problems.
And the game has to be considered a memorable one for Longstaff who got to make his first start in the top flight. It looked set to be a daunting challenge for the 21-year-old as he lined up alongside the struggling Isaac Hayden and was tasked with taking on Jorginho and N'Golo Kante.
But Longstaff acquitted himself superbly at Stamford Bridge. His performance certainly provided no indication that he was making his full league debut as he looked more than comfortable on that stage.
Some of his passing was ambitious and occasionally ventured into the sublime, and plenty of supporters are adamant that he must keep his place in the side for the coming weeks as it was one of the finer midfield displays that the fans have seen in a while.
Here is what some of the supporters made of Longstaff's performance...
Have to say Sean Longstaff impressed me yesterday, a mature performance from the young lad in a tough game. His distribution was superb, he has a bright future ahead of him. #NUFC— Graeme Bell (@GraemeBell_NUFC) January 13, 2019
But Sean longstaff proved me very wrong the kid didn't look slightly out of place big future ahead #NUFC— Lee wale (@Leewale1983) January 13, 2019
Let's talk Longstaff. Thought the lad coped with the weight of expectation very well and showed that he can be trusted as a genuine starting option for us going forward. Streets ahead of Hayden.— (@TheMackemSlayer) January 13, 2019
Shaun Longstaff looked at home in the Premier League today against 150m worth of opposition. Boys a player. Anyone thinks otherwise, needs a long look in the mirror. #nufc— Mark Rutter (@CoachRuts) January 12, 2019
I am very delighted for Sean Longstaff for making his full premier league debut for @NUFC . He put in an impressive performance today. The next person i want to see see in the team is Elias Sorensen— Oba Adeola Amokomowo (@Amoky) January 12, 2019
I think Longstaff did class today, looked like he could keep up and gave it 110%, credit to him— JS (@JJS__1) January 12, 2019
Longstaff should start every week with Diame or Shelvey beside him, he can really become a great player— Adrian™ (@Adrian____29) January 12, 2019
Longstaff was fantastic today. Quality performance and unlucky not to get a point.. #NUFC— Kevin Watson (@watson1993) January 12, 2019