#4 Nemanja Matic
The unsung hero of Chelsea's title triumphs of 2014 and 2016, Nemanja Matic's move went under the radar compared to the other high profile moves made by United, and similarly, while everyone has been raving about United's attack and improved defence, one simply doesn't realize the importance Matic plays in the team, which is often overlooked.
Matic's reading of the game and his knack for playing the right ball in unleashing quick counters have always been known to Mourinho, who knows how to make the best out of the lanky Serb from his time at Chelsea. Matic combined formidably well with Paul Pogba and ensured that United got off to a flyer of a start before injuries to Pogba and various key members came to the fore and created a slight roadblock to proceedings.
Even then, Matic has remained composed and has proven to be a figure of steel in midfield once again and will be crucial to United's title challenge and their run in the Champions League.
The Serb continues to be Mourinho's strongman in midfield as he was at Chelsea and even though a number of combinations have been tried at the center of the park by Mourinho at United due to injuries and otherwise, Matic has been a constant presence at the heart of the pitch. A wall in front of the defence, Matic continues to perform at a top level and at 29, his experience and presence shall be all the more important going into the business end of the season for Mourinho's United.