Personally I think this is what’s happened to us under Mourinho:
Around the time Poch was sacked the mood around the squad was awful - 2+ years of backward momentum, brick league form entrenching disappointment of losing a CL final, everyone knowing there were several players who didn’t want to be here, and the Poch era having ended without a trophy.
Then we got a bit of a new manager bounce under Mourinho, which got us close to 4th.
But then we had lots of injuries (most damagingly to Kane), and our performances and league position went massively backwards - end of bounce.
Then we had a weird covid-induced break, which I thought might have re-energised the players, but maybe instead just allowed a lot of the players’ morale at the club to fester (based on the disappointing last 2+ years and the disappointing last 10 matches).
Then everyone came back to the weird and deflating experience of playing in an empty stadium, without the noise of the fans to turn their morale around.
And I can’t imagine Mourinho’s dour, tough love approach is helping to turn around this group of players - many of whom have been here for ages and probably just want a fresh start at another team due to all of the above.
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Personally I think our best bet is therefore to sell any of Kane / Alli / Son / Ndombele who understandably don’t have their heart it in here (Ndombele for different reasons to the others), and use that windfall to buy some young, hungry players that are excited at the thought of playing under one of the most successful managers of recent times in Mourinho. (And then when he fails, we’ve still got a decent young squad for a new, younger manager the following season
)