I can understand if He's only played like 8-9 games this season and wants to leave. The reality is He played much more than that so now it's up to him, fight for your spot or leave, his choice. He can't just say "Well the club bought someone better and older than me so it's pointless for me to be here" and uses it as an excuse. When it was only between him and Rashford, there was no fuss because maybe He thought He had a chance but when someone in the caliber of Sanchez came, the rumors of him leaving were appearing everywhere. That's not the kind of mentality I want from a Manchester United player, if someone's better than you, learn from him, take your chances, You have age and talent on your side.
The comparison with Ronaldo is laughable, not only from talent point of view (Ronaldo was 19 when He tore PL defenders a new arsehole) but also from mentality point of view. One is a clear winner, the other started to whinge when the club bought someone better than him. As I said, it's an unfair comparison and people should stop using Ronaldo as an excuse for Martial to be treated as "someone special". SAF treated Ronaldo differently because He knew He had a real world class talent in his hands and He did that after Ronaldo had proven himself to be a world class player, Martial is still nothing in comparison.
I hope Martial will remain a Manchester United player next season. The talent is clear, the mentality? He needs to show it more.