Keeping his cool and heads down hasn't done any good to him. All it earned him is regressed after coming from a hot season.
A player who came from his debut season with us possessing his talent underby normal circumstances with a manager who has faith in him would have improve last season even further and this year he should have been already properly established as a top player, playing for his club and country.
Mourinho mismanaged his last season, destroyed his confidence by never rewarding him and publicly criticizing him. This year things are looking the same so far.
All this will lead to is people lying though their teeth how Martial failed when given his chance while trying to absolve Mourinho of any blame, same Mourinho the serial mismanager of young talents.