What does this formation bring to the team?
Martial will take off some goal-scoring burden from Romelu Lukaku. The two strikers upfront along with an equally attack-minded Alexis Sanchez gives the team better offensive threat. This also provides a better defensive stability to the team and overall improves the balance of the squad.
Ernesto Valverde shifted Barcelona to a 4-4-2 (flat) formation ahead of this season and has seen immense success already. Maybe, it is time for Jose Mourinho to do the same. This will reduce the playing time of Jesse Lingard, but it should be noted that it would be for the greater good of the team.
Marcus Rashford can serve as a good backup to Sanchez, while also providing some good competition to Lukaku and Martial for the striker's spot. Lingard has shown that he can play as a midfielder too, as his off the ball movement and tendency to create space for other forwards will help the team overall.
It would be a conservative approach, but the same was said about Valverde ahead of the season. The truth is, the 4-4-2 (flat) formation is something that helps the team with more defensive cover, while it also increases the offensive activity of the team.
It is necessary to roll back the years and take a leaf out of Sir Alex Ferguson's book to bring out the best from this United squad.
Here's how the side would line up in said formation: