Martial has played with number nine on his jersey shirt since his arrival at the Premier League club last season, however Swedish star Zlatan Ibrahimovic recently signed for Man United and has been given the squad number, leaving Martial with number 11.
It is hugely significant for the Frenchman who has been using the 'am9' name to promote his own personal brand in a similar fashion to how Real Madrid superstar, Cristiano Ronaldo, has used his number seven shirt number in his CR7 marketing endeavors which have included underwear, headphones and football boots.
Ibrahimovic is renowned for his outspoken and tenacious personality and confirmed on social media that he has taken the coveted number nine for himself.
Martial has used am9 across his website and even has 'am9' embroiled on his own Nike boots.
The change will undoubtedly affect his ability to market himself and appears to have frustrated the 20 year-old who subsequently unfollowed the club on social media. He also changed his profile picture on Facebook to an image showing him wearing the number nine shirt during the FA Cup semi-final at Wembley.