Manchester United crashed out of the Carabao Cup in utter humiliation, stunned by League Two side Grimsby Town after a nerve-shredding marathon shootout at Blundell Park.
The hosts tore into Man United with fearless energy, scoring twice inside the opening half-hour to send the home crowd wild.
The Red Devils clawed their way back through Bryan Mbeumo and Harry Maguire to force penalties.
Matheus Cunha then spurned the chance to seal victory from the spot, dragging the tie into sudden death.
In a dramatic climax, Bryan Mbeumo smashed his penalty off the crossbar, sparking bedlam as jubilant Grimsby supporters flooded the pitch to celebrate one of the greatest nights in their history.
Speaking to Sky Sports, former United defender Phil Jones admitted that he was left baffled by the tactical change Ruben Amorim made when his side was trailing.
“When he changed and put Mason Mount in that position, they still went with a back five, but they were building with a back five against Grimsby, who were sitting on the edge of the box.
“Your spare man was almost in build-up when you needed that spare man sort of further higher up the pitch to make an overload out wide or through the middle.
“He’d (Matthijs de Ligt) be the one joining in, and with the greatest respect to him, he should have an attacking player getting into the box, where a lot of the time it was a defender, an extra man, that it just seems crazy that he is so wedded to this formation, at all costs and at any circumstance in a match.”
It was truly embarrassing to see Mason Mount playing as a left wing-back after coming off the bench in the 64th minute.
The Englishman had looked bright in his first two outings, knitting play together with clever combinations in attack.
His sharp runs and delicate flicks had the potential to unlock Grimsby’s stubborn backline.
Yet Amorim inexplicably sacrificed that creativity, exiling him wide just to satisfy his formation.
If the head coach had used Mount to create an overload in the box, the game could have been ended in normal time.
Not only Mount, but Matthijs de Ligt played out of position.
The Dutch international often found himself in scoring areas.
He even tried his luck with two efforts, but both flew harmlessly over the bar.
That was the role crying out for Mount, not a centre-back.
This was yet another in-game management blunder from the Portuguese coach, who has already made several errors in his short United tenure.