#4 Andreas Pereira
Perhaps the most un-Mourinho player in this list, the stylish playmaker Pereira seemed set for a big season after promising showings during the summer's preseason tour. After impressing in La Liga with Granada and Valencia in the two previous seasons, the Brazilian returned to Old Trafford ready to stake his claim for a first-team spot.
Since then, however, he's found only 2 starts and 1 substitute appearance in the league. Mourinho has previously frozen out quality flair players at previous clubs, like Mohamed Salah and Kevin de Bruyne at Chelsea, preferring those who fit into his conservative system, and Pereira, unfortunately, seems to be suffering the same way.
Expensive new signing Fred has blocked his path to the starting eleven but his fellow countryman has struggled to settle into English football and its physical aspects. Mourinho, sadly, hasn't trusted those on his bench like Pereira to make a difference.
Manchester United have a rich tradition of youth, going back to the 1990's when David Beckham, Gary Neville, and Paul Scholes burst onto the scene together, and one has to think that Sir Alex Ferguson may have been more trusting of youngster like Rashford and Pereira to galvanise his team.
The Old Trafford support have voiced their concern about their team's boring style of play recently and Mourinho should know that a player like Pereira could rectify that.