Erik ten Hag's side have been far from their best throughout both of their opening two matches of the campaign.
Many feel they were lucky to claim a 1-0 win over Wolves before they fell to a 2-0 defeat away at Tottenham on Saturday.
However, preparations for the visit of Steve Cooper's side appear to have taken a hit with reports emerging that they lost 3-0 to Premier League newcomers Burnley on Wednesday.
Reports claim that United had experience in the starting XI with Jonny Evans, Scott McTominay and Anthony Martial featuring.
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Youngsters Hannibal Mejbri, Alvaro Fernandez and Facundo Pellistri also played in the defeat, with the former involved in first-team training.
It may only have been a behind-closed-doors friendly at their Carrington training ground, but fans have been left concerned.
One took to X and with a series of laughing emojis, saying: "We are finished."
"It's gonna be a long season man," added another, who clearly isn't hopeful of their chances for the remainder of the 2023/24 campaign.
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A third said: "Can't win a friendly, can't win a league [game] comfortably, no hope of new arrivals. United fans are in for a long ride!"
"We don't play friendly games FC getting embarrassed both in public and behind closed doors," said a fourth who also saw the funny side of things.
United are by no means the worst team in the Premier League so far this season given they sit 12th with three points.
However, fans will be hoping to quickly see an improvement in performances before their rivals begin to race ahead of them.