The Frenchman has started the last two matches on the bench and struggled for consistency all season.
But he was named in the starting line-up against the Hornets at Old Trafford in place of Marcus Rashford.
Anthony Martial starts for Man United against Watford, and Twitter loves it
Sat, February 11, 2017
Anthony Martial is named in Manchester United's starting XI to face Watford, and fans are delighted
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Manchester United fans are delighted to see Anthony Martial in the starting XI
And speaking prior to the match, Mourinho praised the Frenchman for his hard work.
He told Sky Sports: "I just feel Martial is working really hard, without having a chance in the past couple of weeks.
"And we play on Thursday again and Marcus Rashford is almost playing every match, not starting a lot but playing and I think Anthony deserves this chance."