The French striker came off the bench to net the all-important winner in the 81st minute at Old Trafford and secure the three points for Mourinho’s men.
Martial has been in good form for Manchester United so far this season, having scored four goals in the Premier League this term.
And the forward has lifted the lid on what Mourinho told him to do before he came on as a substitute at Old Trafford on Saturday.
Speaking to Sky Sports after the game, Martial said: “The manager told me to find space.
“I know that Romelu Lukaku is good with his head and I found the space and scored.”
He added: “We lost the last game. It was important for us to win and I am happy to score.”
The win was a welcome one for Manchester United and it allowed them to keep pace with Manchester City in the race for the title.
The Red Devils headed into the game on the back of their shock 2-1 loss to Huddersfield Town last weekend.
Manchester United now switch their attentions back to Champions League affairs and their home clash against Benfica at Old Trafford on Tuesday night.
Mourinho is aiming to become the first manager since Sir Alex Ferguson to lead the Red Devils to the Premier League title since 2013.
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