#1 Jose Mourinho missed a trick with his strikers' selection

After revealing in the pre-match press conference that some United players are "not good enough" at his disposal, Mourinho stayed true to his words and dropped Martial and Rashford to the bench. This meant that United started with Alexis Sanchez and Jesse Lingard up front.
In a 3-5-2 system with a place for two out and out strikers, the manager made his intentions clear by playing two auxiliary forwards in an unnatural position. Both Lingard and Sanchez have a natural tendency to drop deep to get involved in the game.
United hence lacked a runner that ran in the channels or a presence in the box to keep the defenders occupied. Paul Pogba had a lot of time on the ball but had no players ahead of him taking dangerous positions. With Sanchez and Lingard dropping deep, it all became too crowded in the middle which ultimately played to the advantage of West Ham.
Jose Mourinho should have started with either Martial or Rashford against the Hammers with Lingard and Sanchez behind the striker. It would have given United the much-needed freedom and movement in the final third to trouble the opponents. Meanwhile, Romelu Lukaku's absence was again clearly felt by United from start to finish.