Newcastle United fell to their eight defeat in their last 10 league games, putting the Magpies' Premier League status in further doubt.
Steve Bruce's men were not awful on Manchester and they did have some joy as they pressed high up the pitch but individual errors cost them dearly.
Marucs Rashford fired Manchester United into the lead on the half hour mark in a move that was not Emil Krafth or Karl Darlow's finest hour.
Allan Saint-Maximin fired his side level just six minutes later and at 1-1, Newcastle gave as good as they got until Nemanja Matic was inexplicably herded into the penalty area before putting a ball into the box. Bruno Fernandes flicked it on to Daniel James who somehow was completely unmarked and finished well one on one against Darlow.
A poor challenge from Joe Willock inside the area gave Fernandes the chance to put the game beyond Newcastle and he took full advantage, slotting the ball past Darlow.
Relegation worries intensify on Tyneside
Newcastle played well for large parts of the game at Old Trafford but unfortunately the time to be encouraged by decent performances is well and truly gone, the Magpies have to start picking up points sooner rather than later.
With Fulham beating the Premier League's basement club Sheffield United 1-0 on Saturday, Bruce's side are just three points ahead of the bottom there with a significantly worse goal difference to boot.
Next up for the toon is Wolverhampton Wanderers in the late kick off on Sunday in a game that is now undoubtedly a must win.
If Newcastle can pick up maximum points, it would increase the gap to six points as the Cottagers aren't in action until Sunday.
It is still in Newcastle's hands and their next three after wolves sees them take on West Bromwich Albion, Aston Villa and Brighton and Hove Albion, if the magpies' struggles continue through this run; a third relegation of the Mike Ashley era would loom large on Tyneside.
Is it time to see Martin Dubravka back in the starting XI?
Darlow was poorly beaten at his near post for Rashford's opener which puts further question marks over his place between the sticks.
Martin Dubravka has been mr reliable for Newcastle since joining from Sparta Prague in 2018.
Whilst Darlow has been a brilliant stand in for the Slovakian international but mistakes seem to have been happening more frequently since Dubravka has been back available with the English shot-stopper looking like he is feeling the pressure.
Few goalkeepers in the league have been as impressive as Dubravka in the past few seasons and last season, his performances were rewarded by winning the Newcastle United Player of the Season award.
He made more saves than any other Premier League 'keeper in the 2019/20 season and was a huge reason why Newcastle were able to stay in the division comfortably.
Is it time for Steve Bruce to bring him back into the fold as his side battle against relegation?