Mourinho 'never gave up' on in-form Martial
Martial has scored in four consecutive Premier League games and won the club's player of the month award for October.
He was also named in Didier Deschamps' latest France squad this week having missed out on selection for the World Cup, Les Bleus triumphing without him at Russia 2018.
With Romelu Lukaku struggling to recover from a muscle injury in time for Sunday's Manchester derby, Martial could play a key role for United at the Etihad Stadium.
Martial's long-term United future appeared bleak ahead of the 2018-19 season after he was criticised by Mourinho for not returning to pre-season training quickly enough following the birth of his second child.
Reports indicated Mourinho was willing to allow Martial to be sold to finance upgrades elsewhere in his squad, but the Portuguese has denied ever losing faith in the 22-year-old.
"I never gave up," Mourinho told MUTV. "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."
Jose knows best. pic.twitter.com/w3NOwzJxTn
— Manchester United (@ManUtd) November 9, 2018
Mourinho is hopeful Lukaku will be available for the derby after he trained on Friday, the striker missing United's last two victories, over Bournemouth and Juventus.
But reports have indicated Paul Pogba, who struck a brace in April's 3-2 comeback win for United at the Etihad Stadium, could be a doubt.
The France international was not pictured in a training video the club published on social media.
Plenty of smiles in today's training session!
Now, our focus turns to Sunday... #MUFC pic.twitter.com/OdkLCF9HXg
— Manchester United (@ManUtd) November 9, 2018