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Paul Pogba departs Old Trafford a riddle, wrapped in a mystery, inside an enigma. It was not ever thus. Six years ago there were certainly questions that hung over his return to Manchester United for a world record fee, but they were of the "is he going to be the best midfielder of the world" and "will he be the man to turn the Red Devils into serial title contenders" variety.

Those have now been answered... and not in the affirmative. While several top teams are eyeing up Pogba, now that his inevitable departure on a second free transfer has been confirmed Juventus are expected to be at the head of the queue, there will be one question at the forefront of their minds. Was Pogba's decline over the last few years down to the situation at United?

Wherever you lay the blame, Pogba's performances have certainly been underwhelming. How often across the past six seasons has Pogba been the best player in a big game? The Europa League final immediately comes to mind, as does that 3-2 comeback win to deny Manchester City the Premier League title, at least for a while. The 804 word exit statement-cum-eulogy on United's website points to enough to suggest that the talent was there.

If at times it felt like the most virulent pundits would only accept Pogba when he delivered 10/10 performances on a weekly basis, the reality of his latter years at Old Trafford was one of fleeting returns and underwhelming output. Across the last three seasons of Premier League football he averaged 0.31 combined expected goals (xG) and expected assists (xA) per 90 minutes. That is not bad but it is not as good as the likes of James Ward-Prowse, Matthias Jensen and Pascal Gross. Kevin De Bruyne, the man he was supposed to vie with for the title of the Premier League's most dominant midfielder, has more than doubled that return at 0.65.

There was a time, even at Manchester United, when it genuinely seemed Pogba might belong in that highest of echelons. In 2018-19 he returned 0.6 xG+xA per 90 (the best tally for a midfielder that year) across 35 games, ending the Premier League season with 22 goal involvements. His place in the PFA Team of the Year was the subject of no little debate, how could it not have been when Pogba cannot even get a haircut without pundits bloviating on his attitude, but it should not have been. Given a defined role by Ole Gunnar Solskjaer as a ball carrier with licencs to stay near the top of the box, Pogba excelled. 

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The issue was rather that few others did. United ended the season in sixth, a far cry from the club they had promised to be when he joined. That summer could be, Pogba said, "a good time to have a challenge elsewhere." He was right. His club had not become what they promised to be. 

At the time Pogba first returned to United from Juventus they were said to believe that their chief selling point to him was "a stable environment, a serial trophy-getter [Jose Mourinho] as their manager and a newly assembled side that will begin the season as genuine candidates for the Premier League title." Aaah well, nevertheless.

Across six years Pogba's United managers have been: a serial bridge arsonist who still wins trophies, the man who got Cardiff relegated from the Premier League, Michael Carrick (I've not got much cutting to say about him, he seems a good guy and that 67 percent win ratio speaks for itself) and an interim boss they hired to be a consultant who will depart having done zero days of consulting. Passing Erik ten Hag like ships in the night bumps Pogba's managers up to five, a neat summation of how this has been anything but a stable environment. 

Of the players to start more than 10 league games in his first season back at Old Trafford only David de Gea and (perhaps) Marcus Rashford will still be there next season. No matter the false dawns in 2020-21 or the second place that was nearer to sixth in 2017, United were never genuine title contenders. There were precious few facets to life in Manchester that remained the same, only turbulence. Well, turbulence and ownership paying itself dividends.

Even on the pitch, Pogba, whose nine separate injuries since the start of 2019-20 ought to offer cause for concern among prospective buyers, never had a defined role for long. Given a run of games in any one spot, even the left flank, and he would trend towards excellence, but his versatility was no less a curse than a blessing. One need only see how he thrives for France with a defined role alongside N'Golo Kante, to see the benefits of stability, yet the cast of characters around him was constantly in flux, never bringing a more defensive minded player he could anchor midfield with.

To that, Graeme Souness might say, the very best can adapt. De Bruyne, for instance, has had seasons as a right winger, a false nine and a free eight but he has rarely failed to excel. But City have surrounded their Belgian with excellence. United keep throwing money at the middle of the pitch, praying that some of it might stick.

The reality is that when Pogba has played a defined role with club or country he has excelled. One might argue that the very best can excel even in unfavorable climes but it rather misses the point. Why would you not want to design a system that exploits this gaudiest of talents?

Or, why wouldn't you have, at least. Because, while that might have been true three seasons ago when Pogba was a world champion with several seasons of excellence in the rear view mirror, now the 29 year old looks to be hamstrung by injuries, his output fading almost as swiftly as his desire to put on a Manchester United shirt. Would you want to redesign your midfield to exploit him? 

Pogba exits United mired in somewhat of a chicken and egg problem. Until he finds himself in an environment conducive to success it is hard to know exactly how far towards greatness his talents can still get him. But, until he proves that his reservoirs of talent remain, it's hard to justify creating the environment to exploit them. It's quite the riddle indeed that Juventus, or whomever else might dangle a giant check, will find themselves in.