I think it is pressure, as in he has Performance Anxiety.
I think that he looks brilliant in training, when there is no pressure, and that is why Ole picked him to start. But then in the real match, the pressure gets to him badly and he cannot perform. He looked today like he was hyperventilating and thus could not run at all.
I think as well if he went to Bayern or PSG he would suddenly look world class again because Bayern and PSG basically have a monopoly in their retrospective leagues and thus there is less pressure on him. He would put less pressure on himself to play good and hence would play better.
Do you ever notice that when we are winning by three or more goals, he suddenly comes good. Everything starts clicking. That is because the pressure is now off. No pressure, equals no anxiety, which equals a better performance.
At Juve he looked good for exactly what i said in the third paragraph, in that six or seven years ago, when he was at Juve, they were just light years agead of everyone else in the league and thus there was less pressure on him.
Personally i think we should let him go.