Can't believe you can say something like that, I presume with a straight face.
Who has Jose improved as a player? That is also why Jose always wants the finished/proven product because he doesn't improve players. In actual fact to a degree(not blaming Jose completely) I would say he has held Martial back with his style of play and continually shunting him around in the team or dropping him to the bench.
If Utd do sell Martial, I am sure it will be another KDB, Lukaku, Salah story, except the mistake will be even bigger. If you look at his pace, his movement and dribbles on the ball, with the right coach he could be the next Neymar or maybe even more. That is also why when he was sold to Utd with all these crazy add-ons/bonuses included in his contract, because they knew he has all the potential to reach those heights.
If Jose showed half the faith he shows in Young, Fellaini, Lukaku, Mc Tominay and Pogba (up until the last 2 months), Martial's stats would be even higher.
I for one don't believe Jose will sell Martial but looking at the way he has been treated and is being treated at the moment, I could quite easily see Martial asking for a transfer. Should one of the big European clubs come along, he will be gone.