Imagine being Martial. You come to the club as a potential striker and scores against Liverpool on your debut. You're the only promising young attacking player they have so you get care free love and a song to go with it. Then a young local striker emerges and you get pushed out wide to accommodate him. You then get a new manager who takes away your number completely and have you prove yourself worthy as a wide midfielder fighting for a spot against the only promising young attacking player in the squad. After struggling with the trust of the manager, injuries and lack of playing time a new manager comes in, gives you the number 9 and sell off all his competition. 4 months in and a new local young attacking talent comes through, proving himself to be absolute born to play the position you want to claim. Then you have Keane himself visiting trying to intimidate you for no apparent reason, before you sit yourself in the car to have a relaxing drive home and you hear rumour talks of Haaland junior to United on the radio.
It's all connected and it's never looking too good for Martial
Might explain his mug.
Even when we aren't performing like a top club some players do still get the top club treatment, and credit to our academy for most of it. He needs to just get on with it and get in form then he'll bang them in 10 games in a row.