Losing embarrassingly against a weak team will certainly make the mentality of the Manchester United team very depressed, especially with the many insults from the fans which will make it difficult for them to recover, so I will not expect anything more from Manchester United this season, I am sure they will not be able to start the process of being better even a little compared to last season.
I also find it unbelievable that this Manchester United squad could lose to a team in the Premier League's fourth division. Despite having far more depth than that team, Manchester United's squad was completely outclassed, but all that was rendered useless when Manchester United were eliminated from the Carabao Cup on penalties. And based on this result, I can't expect Manchester United to be in better shape this season, as they have faced teams far stronger than Grimsby Town in the Premier League.