Carabao Cup second round: Grimsby Town 2 (Vernam 22, Warren 30) Manchester United 2 (Mbeumo 75, Maguire 89) [Grimsby win 12-11 on penalties]

Manchester United – bloody hell: after a chaotic display in regular time that somehow pulled them back to 2-2 and penalties, Ruben Amorim’s rabble lost a fevered shoot-out 12-11.

When Bryan Mbeumo’s kick smacked Christy Pym’s bar after Meathman Darragh Burns buried his second shot from the penalty spot for Grimsby, the home side entered the nirvana of a cup-shock for the ages and the faithful’s song of “Oh when the Town go steaming in” sweetly summed up what they did to United.

United were two down by the interval and appeared heading out after Charles Vernam and Tyrell Warren first-half strikes had the 20-times English champions facing a humiliating oblivion from the Carabao Cup.

But a 75th-minute Mbeumo finish handed United a lifeline before Maguire’s stooping header squeezed in at the near post took the game to the penalty lottery.

Amorim’s men lost it, so, let the inquest begin.

On a smooth green sward that allowed no excuse the XI Amorim sent out in search of an opening win of the campaign that showed eight changes. Alongside Mainoo, Benjamin Sesko, André Onana, Harry Maguire and Manuel Ugarte were other headline acts given first starts and who failed to quieten a rambunctious home fancy in a chastening 45 minutes.

Cameron McJannet’s clatter on Amad Diallo that left the No 10 collapsed telegrammed what David Artell’s team were about. Then, when Cam Gardner rose to “oohs” from the Mariners congregation the centre-forward had a chance to beat Onana but headed into his gloves.

Grimbsy's Geza David Turi is challenged by Manchester United's Harry Maguire. Photograph: Shaun Botterill/Getty Images

Grimbsy’s Geza David Turi is challenged by Manchester United’s Harry Maguire. Photograph: Shaun Botterill/Getty Images

United were under the pump. A Vernam corner from the left threatened to arrow over Onana and in before the goalkeeper scurried back and tipped over.

Artell had drilled his men to tap the ball about around halfway then up tempo to stampede at United. Or rush up to a man in red to squeeze them: precisely how they took the lead.

Under pressure Diallo miscontrolled, tried to retrieve the ball, he and Ugarte bumped into each other, pratfalled, and Grimsby tookover. A quick right-left diagonal from former Republic of Ireland under-21 Burns turned United, put Vernam in, and he beat Onana at his near post: the Cameroonian should have saved so here was the latest howler from a man between United’s sticks.

Amorim fielded repeated volleys of “you’re getting sacked in the morning” from an ecstatic Grimsby support whose volume matched the whirling energy of their men. Next all entered dreamland.

A short Vernam corner on the left was returned to the No 30 whose delivery sliced in menacingly. Onana rose above a thicket of players and, farcically, missed a clearing punch, the ball dropped to Tyrell Warren, who rolled home against the club he left in 2019.

This time the chants from fans were a cutting, ‘Can we play you every week,’ and ‘Premier League/you’re having a laugh’. They had a point. Grimsby were in cruise control, toying with their shell-shocked guest.

When Sesko managed a header you were reminded that United were allowed to attack, too.

At the interval Amorim had to start earning his lucrative wage.

Manchester United's Benjamin Sesko misses a chance in the final moments of the game. Photograph: George Wood/Getty Images

Manchester United’s Benjamin Sesko misses a chance in the final moments of the game. Photograph: George Wood/Getty Images

Tyler Fredericson, Patrick Dorgu and Ugarte were hooked for Matthijs De Ligt, Bryan Mbuemo and Bruno Fernandes. Calling for the cavalry crystallised how dire United were. An early foray had Cunha nodding into Pym’s hands. This was positive but Amorim’s face broke to bitter disappointment.

In rain bucketing down Grimsby poured forward and a Burns effort went for a corner as, again, United’s noses were bloodied.

The downpour, becoming biblical, had the surface greasy and skiddy – perfect for a side on a mission to pen an immortal chapter in the club’s history.

United were jammed in a catch-22 of needing to press in the quest to pull a goal back while not daring to leave space for Artell’s ruthless unit to prosper once more. Example: Grimsby moved along their right, swapped passes, and lifted a highball in – the omnipotent Vernam leapt and bounced a header into the ground and for a moment you wondered if Onana might mishandle. But, he clutched the ball safely.

So far Amorim’s substitutions had failed to engineer any dominance or create any regular openings. When Diallo, down the right, was flagged offside Amorin dipped his head in anguish – a regular feeling for him. Better was a Fernandes shoulder-dip-then-unload: the ball skimmed across the water for Pym’s left corner but the keeper dove and held admirably.

Amorim, despairing, sent for a favourite player, Mason Mount, who replaced Ayden Heaven.

When Mbeumo’s strike came United still seemed a universe away from levelling. But they do possess spirit, as personified by Maguire with his equaliser. – Guardian