After starting just one of United's opening six league games, he has scored five goals in his last four outings to win back the trust of both Mourinho and national team manager Didier Deschamps.
And speaking on Martial's U-turn at the club, Mourinho has revealed he set a hard path for his player in order for him to realise his "phenomenal talent".
Martial, 22, was not in the France squad that won the World Cup in Russian Federation.
"I never gave up", Mourinho told the club's official website.
"We're still talking about a young player who, I hope, is in the process of gaining a certain maturity", said Deschamps.
Deschamps acknowledged Martial's struggles to maintain his best form in the past have held him back at times.
'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. "If he is there, it's also because some players are injured".
"That can be seen on the pitch, with the importance he's taken on in recent weeks in Manchester, in the head of Jose Mourinho, and what he's doing on the pitch".
Martial has scored five times in his last six appearances for United, with the 22-year-old bouncing back from a hard start to the season to become a feature in Jose Mourinho's first XI.
Manchester United visit Premier League Champions at the Etihad Stadium in a derby clash and ex-England midfielder has heap praise on Martial by insisting that claiming that former Monaco man could overtake Chelsea and Belgium skipper Hazard in world football rating.
And he has been further rewarded for an upturn in his performances with a place in the France squad for their Nations League clash against Netherlands and a friendly with Uruguay.