Manchester United may be kicking themselves for not appealing after Grimsby were penalised for fielding an ineligible player in their legendary Carabao Cup second round triumph over the Red Devils. The Mariners were slapped with a £20,000 fine for playing Clarke Oduor in the memorable victory.

Despite having grounds to file a complaint, United chose not to, allowing Grimsby to progress to the fourth round of the League Cup after defeating Sheffield Wednesday 1-0 on Tuesday evening.

United manager Ruben Amorim is feeling the heat following the team's League Cup exit and the crushing 3-0 defeat in the Manchester Derby on Sunday. If United had appealed and been successful, they could have been facing off against Wednesday on Tuesday evening instead of Grimsby, who could have been booted out of the tournament.

A tie against a team currently struggling in 23rd place in the Championship could have been just what the doctor ordered for Amorim. A game against Wednesday would have been seen as winnable and could have potentially put United in the fourth round, with dreams of Wembley glory providing a much-needed boost for the beleaguered boss.

However, United's decision not to appeal allowed Grimsby to advance, with their win over the Owls on Tuesday evening adding insult to injury for United after their disappointing start to the season, reports the Manchester Evening News.

United are currently languishing in 14th place in the Premier League, one spot up from their final position last season, and have secured one victory in four matches this campaign. Amorim had been hopeful of leaving last year's disappointments behind, particularly following United's Europa League final loss to Tottenham Hotspur.

However, despite an influx of new talent, United's midfield seems sluggish and their strikers are lacking service. Their defence appears increasingly vulnerable each week, as players struggle to adapt to Amorim's preferred 3-4-3 formation, a strategy that has yet to prove successful at Old Trafford.

Despite these issues, the club reportedly still believes in Amorim's capabilities, although concerns are mounting. Reports state that some first-team squad members are beginning to question their manager, suggesting that the former Sporting CP boss is too rigid in his philosophy rather than focusing on improving results.

United's decision not to contest Grimsby's continuation in the cup, while commendable, could serve as a pivotal moment for the club, given the favourable draw in the third round.

Grimsby introduced Oduor against United in the second half of their cup tie, with the player having joined on loan just the day before from Bradford City. The club later discovered that the player had been registered one minute and 59 seconds after the 12:00 deadline.

After United staged a comeback from 2-0 down, the match went to penalties. Oduor's penalty was saved by Andre Onana, resulting in Grimsby winning the lengthy shootout 12-11.

However, Grimsby subsequently reported their own breach of rules. They stated that the "club's non-compliance was not deliberate with no intention to deceive or mislead".

The League Two team was slapped with a £10,000 fine, with an additional £10,000 suspended until the end of the current season. The EFL stated that the decision to fine David Artell's squad was made after a "comprehensive review of all the evidence and considering prior decisions taken in respect of offences in the League Cup".

Grimsby Town punish Man Utd even further after Carabao Cup appeal decision - The Mirror