I think people need to understand that the "uncertainty" around Pogba has nothing to do with him being at Juve. There is "uncertainty" around Messi, Neymar, Ronaldo and the likes as well because those are the names that sell.
If we want to be free of transfer rumors we need to have a team full of Padoins. In todays football every player and their dog will get drawn to transfer speculation such is the business nowadays.
And even if he went to Real Madrid or Barcelona there would be rumours in a year or two that 'random rich English team' wants him and he want to play in TBLITW, or the other way around, or he wants PSG, it never stops for that calibre. Like you say, even the clearly untouchable Messi has been linked with moves now and then over his career.
The reality of football is that there are no impossible moves, and writers know this, but what they don't cater for is the probability of each one. They can say write anything. We all think that Pogba will leave some day and for a lot of money, so there is no reason to not regurgitate the rumour every summer. Personally speaking I don't see him leaving this summer, not with a driven CL tilt in the plans of the club. Next summer I wouldn't be so sure.
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Can we rule out Pogba saying he wants to leave in the middle of the mercato like Vidal ?
No, that's the reality. And when you consider how important the team spirit and cohesion is and has been for the club now and in the past I agree with the philosophy of the directors to sell ANY player who doesn't feel like his head is completely there for Juventus. You might quieten them down over the course of the season by rejecting such demands, depending on the professionalism of the individual, but can you really expect their best, that extra bit to push us over the line like we have done so many times this season? Ultimately you are just delaying the inevitable if a player has his mind set on a certain club or league or mega salary, whatever motivates him.