Ruben Amorim’s Manchester United reign hit a new low as his side were dumped out of the Carabao Cup on penalties by Grimsby.After the match finished 2-2 after normal time, the Red Devils lost a thrilling shootout 12-11, with Bryan Mbeumo missing the decisive spot kick to give the League Two side a famous win at Blundell Park.GettySummer signing Bryan Mbeumo missed from the spot to give Grimsby a famous win[/caption]Sky SportsThe result sparked a wild pitch invasion[/caption]This was the first meeting between the two sides since 1948, and the earliest stage United had entered the competition in 11 years, when they were thrashed 4-0 by League One side MK Dons in 2014.And history seemed to repeat itself for Amorim‘s side, as they fell to a first ever defeat to a fourth tier side in the League Cup.Despite a strong United starting XI which featured summer signings Benjamin Sesko and Matheus Cunha, it was the Mariners who looked the more threatening of the two sides to begin with.And they put pay to their energetic start in the 23rd minute, when Charles Vernam volleyed home to send the home crowd wild.It was a moment to forget for United goalkeeper Andre Onana, who was slow to react to the shot at his near post.But things soon got even worse for the Premier League giants, and Onana, when Grimsby doubled their lead eight minutes later.Former Red Devils academy player Tyrrell Warren will not have been able to believe his luck, as he tapped the ball into an empty net after the Cameroonian stopper spilled a cross.United were unable to trouble their fourth-tier opponents, who headed in at half time with a comfortable two-goal cushion.Under mounting pressure, Amorim rolled the dice at the interval, bringing on Mbeumo, Bruno Fernandes and Mathijs de Ligt.With the rain lashing down in Lincolnshire, it looked for a long time that United would be suffering a new low after failing to get a win in their first two Premier League games.GettyAmorim didn’t even watch the penalty shootout, which was probably a good thing for him[/caption]GettyWarren put the Mariners in dreamland just after the half-hour mark[/caption]But the substitutions eventually paid off, as £71m summer signing Mbeumo pulled a goal back with a low strike with 15 minutes left.And just as Grimsby looked to be heading for a fairytale result, their dreams were crushed by Harry Maguire right at the death.With United piling on the pressure, the England centre-back rose highest at a corner to head home at the far post, and spare his side’s blushes.This forced a thrilling tie to penalties, where Jaze Kabia, Fernandes, Darragh Burns and Mbeumo all converted the first four spot kicks.But Grimsby then found themselves staring at elimination after Onana saved Clarke Oduor’s effort, before Mason Mount and Diogo Dalot netted to give Matheus Cunha a chance to seal the tie.But the £62.5m signing rolled the ball into the arms of Christy Pym to take the shootout to sudden death.GettyMaguire forced the tie to penalties, as United clawed their way back[/caption]GettyBurns scored Grimsby’s 13th penalty of the night, before Mbeumo’s miss[/caption]Sky SportsThe Mariners fans rushed onto the pitch to celebrate with their players[/caption]The pressure seemed to bring the best out of both sides, as incredibly, each of the next six takers on each team converted to reset a thrilling shootout back to the start.But after Kabia, Fernandes and Burns all netted their second penalties of the night, something had to give.And it was Mbeumo who was the first to falter, as his second effort from 12 yards crashed the crossbar to send the Grimsby fans piling onto the pitch.The result sees David Artell’s side head into the third round, where they will face Championship side Sheffield Wednesday.