#3 Strengthen the full-back positions
Despite players like Luke Shaw, Matteo Darmian and Daley Blind being signed by the club in recent years, it is 2 wingers who were a part of Sir Alex Ferguson's squad, that ply their trade at both fullback positions as undisputed starters.
This is something that Mourinho would not be happy about, no matter how much he praises Antonio Valencia and Ashley Young in public.
Young, who has earned call-ups to the England squad after a gap of 3 years is, in all probability, the best crosser in the team. Despite his high work rate, he is often prone to the odd defensive error and is highly inconsistent.
His understudy, Luke Shaw has made only a handful of appearances for the first team and looks likely to leave Old Trafford this summer. Jose Mourinho clearly is not a big fan of his and has criticized him in public while questioning his commitment.
Antonio Valencia, despite being fast and full of trickery, is not a natural right-back. He has been caught in the wrong position a number of times and his crossing is not up to the mark. Matteo Darmian has featured mainly in cup competitions and is another player being linked with a move away from the club.
Mourinho will be well aware of the quality, or rather the lack of it that he has in the fullback positions, and needs to bring in young and talented players in the summer. Players like Danny Rose, Alex Sandro, Fabinho and Kieran Tierney have been linked with a move to Manchester United.