Grimsby 2-2 Man United (Grimsby win 12-11 on pens): Where do Ruben Amorim's dismal side go from here after humiliating Carabao Cup exit?

They poured scorn on Manchester United from the stands and baited them with inflatable haddocks. They revelled in the latest humiliation of this once great football club and a famous night for Grimsby Town.

Oh, how the locals at Blundell Park loved this and rightly so. What a night for the League Two club and a deserved win in an incredible Carabao Cup tie, one that will go down in folklore in this corner of Cleethorpes.

But what of United, dismal, wretched United? Where do they go from here? The optimism of a summer spent rebuilding and spending big under Ruben Amorim had already begun to ebb after taking just one point from their two opening Premier League games, and now this.

A defeat every bit as humiliating as United suffered on their last appearance in the second round of this competition 11 years ago when Louis van Gaal’s side were humbled 4-0 by League One MK Dons, and arguably any in the club’s modern history. It will take its place alongside Bournemouth, York City and Southend in the hall of shame.

Yes, Amorim made changes but he still started with a team that cost £400million to put together, even with two academy products in Kobbie Mainoo and Tyler Fredricson who cost nothing.

The painful truth for United and their suffering supporters is that Grimsby deserved their win. A team so far out of United’s league that the two clubs had not met for 77 years before this.

United deserve some credit for recovering from two goals down to force a marathon penalty shootout as Bryan Mbeumo scored his first goal for the club since a £71million move from Brentford before Harry Maguire headed an 89th-minute equaliser.

But after Andre Onana looked to have redeemed himself with a one-handed save from Clarke Oduor and Christy Pym had thwarted Matheus Cunha, Mbeumo hit the 26th attempt of the shootout against the underside of the bar to send Blundell Park into delirium.

As United look to clear the decks of fringe players before Monday’s transfer deadline, Alejandro Garnacho, Antony, Jadon Sancho, Rasmus Hojlund and Tyrell Malacia probably can’t wait to get out the place and away from this never-ending circus as fast as possible.

And then there’s Kobbie Mainoo who got the chance he wanted here at probably wishes he hadn’t.

Mainoo walked off United’s team bus shortly after 6.30pm and straight onto the pitch with the rest of his teammates, a pair of white headphones blocking out any external noise, after another day of speculation over his future at Old Trafford.

Could his first game of the season also be the last of a United career that promised so much? Despite the modest surroundings, it felt like a big night for the England international as one of eight changes made by Amorim.

If Mainoo was under inevitable scrutiny at Blundell Park, the same could be said for Benjamin Sesko on his full debut after two rather subdued appearances off the bench against Arsenal and Fulham, and Andre Onana.

The United goalkeeper’s summer has been disrupted by a hamstring injury that allowed Altay Bayindir to take over as No.1, however temporarily, and speculation over his future has not been helped by the club’s attempts to sign Senne Lammens from Antwerp.

With Bayindir struggling in the opening two games, particularly under set-pieces, this was Onana’s chance to reassert his authority and yet he was picking the ball out of the net twice in the opening half an hour.

Could he have done better with the first goal? Possibly. United had come under early pressure and struggled to weather it when Darragh Burns switched played from right to left. Charles Vernam controlled it with one touch and still had enough time to size up a shot which he rifled inside the near post as Onana failed to keep it out.

At that point, Cameron Gardner had already headed straight at the United keeper who had also been forced to turn Vernam’s corner over his own bar, looking every bit as uncomfortable as Bayindir.

That was nothing compared to Grimsby’s second goal which came seconds after another effort was ruled out because it went in off Gardner’s arm.

Onana came out to claim a cross from the left but flapped and barely made contact with the ball, gifting Tyrell Warren an opportunity to tap it into an empty net.

The Grimsby fans could barely believe what they were seeing. Light-hearted chants of ‘we only sing when we’re fishing’ turned to a chorus of ‘sacked in the morning’ as Amorim paced up and down the technical area in a state of equal incredulity.

His team rarely looked like getting themselves back into the game in a disastrous first half.

Amorim had no choice but to send for some big guns at half-time, sending on Bruno Fernandes, Matthijs de Ligt and Bryan Mbeumo to provide some stability and leadership.

Pym made a fantastic save low to his left to keeper Fernandes’ shot from range but United’s first-choice front three of Mbeumo, Benjamin Sesko and Cunha struggled to lay a glove on a fantastic Grimsby defence until Mbeumo pulled one back and Maguire levelled to set up the late drama.