#4. Failure to nullify the threat that is Alvaro Morata
Even though the Spaniard failed to score in any of his last six appearances, Alvaro Morata was an obvious threat against United.
Morata was allowed to have as many as 23 touches in the final third including 10 inside the United box. Even though the Spaniard only managed to get 3 shots away, he was a constant threat to the United defence.
The previous point also didn't help Man Utd's cause. With the wingers pushed so far up, the back three of Bailly, Smalling and Jones was really stretched and often left gaps in the middle for Chelsea to exploit with through balls and the excellent dribbling capabilities of both Morata and Hazard.
Because of this stretching of the back three, United's midfield found themselves dug up inside their own half, which allowed space for Azpillicueta to pick an inch-perfect cross for Alvaro Morata not for the first time this season.