Player hostility and under-performance

There is talk of a rift between recent World Cup winner Pogba and Mourinho.
If there is, then it seems that the events at Chelsea and Real Madrid to some extent (with Ronaldo and Ramos) were foreshadowing current events.
This is just speculation, and Mourinho has said that there is no rift. Additionally, Luke Shaw has lost weight and scored a great winner vs. Leicester City. A schism had emerged between the two but now seems to have receded as Shaw is back to prime fitness.
There also is the issue of Sanchez, Martial, and Rashford, who for varying reasons have not featured as regularly.
Alexis, since joining from Arsenal, has not played to the levels shown at the Gunners. Martial has not kicked on from his joining under van Gaal. Rashford also made his debut under van Gaal and hasn't thus far attained his potential.
The squad doesn't look as harmonious as it could be, but the exact nature of this is moot at best.