#1 The Jose Mourinho factor
Jose Mourinho is regarded by many as one of the most astute tacticians in the world. At one point, he was also one of the best motivators in the game, but that attribute seems to have waned ever since his tenure at Real Madrid.
Another thing the Portuguese is known for is his reluctance to work with younger players. At Real Madrid, he rarely gave Alvaro Morata a chance, while at Chelsea, he refused to guarantee playing time for the former Anderlecht player, Lukaku.
This prompted the Belgian to leave the club on a permanent basis and Mourinho revealed the reason for it.
"Romelu was always very clear with us in his mentality and his approach was not highly motivated to come to a competitive situation at Chelsea. He wanted to be clearly the first-choice striker.”
The former Porto boss is known for his ruthlessness. If Lukaku fails to deliver in a few games, it is very likely that the Portuguese would drop him in favour of someone else, which could damage his morale even further.
For Mourinho, results matter over anything else. If Lukaku is deemed a liability, he will not shy away from wielding the axe.