#4 Ander Herrera
Ander Herrera's importance to this Manchester United team cannot be stressed enough. The winner of the Sir Matt Busby Player of the Year Award for the 2016/17 season was brought to Old Trafford by Louis van Gaal and has managed to be an integral part of both the Dutchman and his successor's team.
The Spaniard found his chances limited at the start of this season. Early in the season, Mourinho had opted to start him out of position as a part of a back three against Tottenham, a move that had been disastrous for United as well as the player. Subsequently, Herrera had been restricted to a handful to substitute appearances until the start of November, when United travelled to Turin to face an undefeated Juventus side in the Champions League.
Herrera's tenacity and work rate were crucial as United handed the Serie A side their first defeat of the season. As United struggled in the league, Herrera started in all of Mourinho's last 4 games, as he brought back much-needed stability in the midfield. It was also a period where he scored 1 goal and also picked up another assist.
On Solskjaer's appointment, Herrera has been allowed a lot more freedom to express himself and the Spaniard has been indispensable in the middle. He has allowed Pogba and Matic to flourish and has quietly done all the hard work for the team. Herrera now has 2 goals and 3 assists from 16 games so far this season and a lot more is expected of him in the coming months.
At the start of January, Ander Herrera is ranked 4th in the race to become the Manchester United Player of the season, for the second time in his career.