#2 Alexis Sanchez's lack of improvement
Alexis Sanchez was in a two-way battle between Manchester United and Manchester City last January with the Chilean finally signing for United after a swap deal got agreed between United and Arsenal. Sanchez was Arsenal's best player, and Wenger didn't want him to leave the Emirates. However. Alexis looked to win trophies and hence joined Jose Mourinho at the Theatre of Dreams.
For many United fans, it was a dream signing as Alexis was a workhorse and a goal scorer which the Red Devils needed at that time. It often takes time for a player to adjust to a new system and he did use the entire second half of the last season to settle down at Old Trafford.
There were big expectations from him as the new season began, but he couldn't live up to it. Even after Ole's arrival, Sanchez still looks like a shadow of the player he was at Arsenal. Moreover, the injuries haven't helped his cause either as the Chilean is gradually heading towards a significant transfer disaster for United.