Ahead of the campaign there was plenty of speculation about Martial's future at Old Trafford and it was recently reported the 22-year-old has rejected a new deal with the club. Per Sky Sports, Mourinho was said to be willing to sell the former Monaco man.
But following a brilliant recent run of form, Mourinho told the United website that his faith in Martial did not yield:
"I never gave up. I never gave up my feelings that this was the right way for him, even if he had to go through difficult moments.
"I knew that for him to become a really top player, he needed to overcome some barriers that I put on the road for him. It is up to his talent, because he has phenomenal talent. It was just a question of him understanding what a top player is because there is a big difference between a top talent and a top player."
In a season of ups and downs for United, the form showcased by Martial on a consistent basis has been impressive, with the young forward excelling in a role on the left flank.
So encouraging has his play been that Martial has been drafted back into the France squad for the upcoming international break:
If he can carry the form he's showcased for United onto the international stage then there's no doubt Martial has something to offer the FIFA World Cup winners.
From the left he has been devastating at times. Martial has searing pace, excellent close control and when he does get into advanced positions he's shown tremendous composure throughout his time as a Red Devils player.
While he's the club's top scorer with six goals in all competitions this term, Martial is having an influence on the game even when he isn't being productive in the final third, as journalist Liam Canning commented after the 2-1 win at Juventus:
Following the arrival of Alexis Sanchez in January, there didn't appear to be a natural spot in the XI for Martial in his preferred left-wing position. However, he's usurped the new arrival in the pecking order, as well as Marcus Rashford who has also been stationed out there at times in his United career.
Mourinho does seem to have built up some trust in the player too:
While the manager clearly feels as though he has had a big impact on Martial's progression, the player himself deserves immense credit for seizing his opportunity during some testing spells for the Red Devils.
The challenge for Mourinho and Martial now will be finding a way of ensuring he can maintain such high standards. If he can do, the Red Devils will be desperate to get that contract extension signed as soon as possible.