Following an impressive first season in the Premier League in 2015/16, Martial failed to replicate his success as he has scored just twice in nine starts this season.
As a result, Mourinho admitted that he had no choice but to replace him with someone who is performing better.
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“I don’t think he lost his focus. I think he just didn’t catch with both hands a big opportunity he had.
“We have still five players for these positions — we have Marcus Rashford, Jesse Lingard, Juan Mata, Henrikh Mkhitaryan and Martial. I cannot give to the same player chance after chance after chance and not consider the effort of the others.
“When I have five players for two positions, I have to praise the good performance. Sometimes I have to take people out of the team. That’s simple.”
All in all, Martial has made 21 appearances in all competitions this season and found the back of the net six times to go with three assists.