Ole Gunnar Solskjaer’s side was expected to return to the top of the Premier League on Wednesday but they were deservedly beaten by the basement boys.
Sheffield United may not be the quickest shooters in town. They may not have come to Old Trafford with much confidence after a sapping, demoralising season.
Before this game, Chris Wilder’s team had only won once in the league in 19 attempts.
But give any team in this division a chance like the one United offered up 16 minutes from time and they may just take it.
And here substitute Oliver Burke did exactly that, driving the ball high past De Gea and into the roof of the net.
The shot took a deflection from Tuanzebe’s knee. Without it, De Gea may have saved it. But it didn’t matter.
It was a big chance but six minutes later it didn’t matter. United didn’t deal with a corner from the right and young Kean Bryan – a former City trainee – leapt between Tuanzebe and De Gea to glance a header in off the far post.
It was an unskilled hour of defending from United and their opponents had committed enough men into the penalty area to capitalise. In many ways, it summed up the night.
On an evening that allowed them to go back to the top of the table, United looked nervous about the task. Slow, unstable and predictable.
Wilder’s players, on the other hand, were bold, fierce, organised and – when their chances came – they were very clinical.
This is not a night that is likely to preface a charge out of the bottom three. They are still 10 points from safety.
But that doesn’t mean they should be pleased with this achievement. As for United and their title ambitions, this feels like a big blow.
Suddenly, with Manchester City on the charge, United trail their neighbours and have played a game more. United to face Arsenal on Saturday while City host Sheffield United. If those results go the way they could, United may be back in the pack. It’s tough at the top, isn’t it?
The winning goal certainly came at a crucial time. United, having trailed at half-time, had just equalised through Harry Maguire. But in truth, the warning signs had been there for the home team right from the start.