2) Instruct the full-backs to attack more
Another area where United have suffered is the lack of attacking impetus their full-backs have provided. Aaron Wan-Bissaka is excellent defensively but rarely gets forward to play crosses or overlap. The same can be said of Ashley Young at left-back, although the veteran is playing only due to Luke Shaw's injury.
United need their full-backs to offer more in attack, play more crosses and overlap with the wingers. Given that both Young and Wan-Bissaka are defensively sound, they have the ability to recover in case possession is lost.
By overlapping, they can create numerical advantages against the opposition's defenders and therefore find space. That in turn would facilitate better crossing for the players in the box as well as open up more space for the wingers to cut inside and shoot.
Full-backs are extremely important in modern football, and United need to utilize theirs to the fullest.