#3 - An Incompatible Attack
At the very start of the season everybody was pointing out the friendship between Lukaku and Pogba and how they could be a very dangerous pairing for other teams in the league, and in the first few games this proved to be true.
Introducing Sánchez to the side in January seemed to be an excellent piece of business by Jose Mourinho, as he managed to trade a player who hadn't been performing for one of the best players in the world.
Unfortunately, something just hasn't clicked, and while Sánchez has been trying very hard to contribute to attacks, the team just doesn't seem to have that close bond they had at the start of the season, and the group of brilliant attacking players is performing far less than the sum of its parts.
Bringing in a new player in January is often difficult, as it doesn't give the manager a chance to reconfigure the team. Martial and Lingard were in great form prior to Sánchez's arrival, but since then Martial has been mostly played on the right, where he seems far less natural, and Lingard hasn't been anywhere near as noticeable (bar his great goal against Chelsea).
With the likes of Lukaku, Pogba, Sanchez, Martial, Rashford, Lingard and Mata, United should absolutely be tearing teams apart, but that hasn't been the case. It might just be a case of when rather than if.