#3 Mourinho's man-management
Is Mourinho adding fuel to the fire? Given his recent comments on how "weak" modern players are.
Possibly. This may not go down very well. But if he is this "bad" and "abusive", why did Luke Shaw decide to stay? Why is Lingard happy to stay, or why are Smalling and Young being offered new deals?
Whilst comments Mourinho makes in the public domain can be terse and abrasive, how he acts in private may be different. Fans nor random observers cannot know the deep goings on in clubs, nor the major intricacies at hand.
However, his actions may not be creating a harmonious unit, and this could be translating into the performances on the pitch.
This is speculation though, but it's clear that rumours of players "downing tools" could materialise if comments he's made in the public domain are not well-received.
In the above video, Rio Ferdinand is right to say that Mourinho's comments can have an effect, though it's subjective for each player involved.