There was already the feeling Sanchez may be facing physical burn-out in his last season at Arsenal. This was, after all, an all-action forward who so often pushed himself into what Arsene Wenger described as “the red zone”, and was playing 38 games in a season as long ago as 2005.

That’s a lot of wear and tear, and one reason why Juan Mata is said to have beaten him in sprints at United. It is all one big reason Arsenal eventually gave the go-ahead to let him go.

So much, then, for the idea that Manchester United got the better end of the deal and one over Manchester City.

Out-of-contract Manchester United players Show all 9 1 /9 Out-of-contract Manchester United players Out-of-contract Manchester United players David de Gea Contract expires: June 2019

Contains one-year extension? No



United automatically triggered a one-year extension on De Gea's contract in November. A new contract for the goalkeeper is considered a top priority. Getty Out-of-contract Manchester United players Anthony Martial Contract expires: June 2019

Contains one-year extension? No



Martial's one-year extension was triggered in December to avoid losing him on a free transfer this summer. The club remain in negotiations with Martial's representatives over a new deal. Getty Out-of-contract Manchester United players Juan Mata Contract expires: June 2018

Contains one-year extension? No



United automatically triggered a one-year extension on Mata's contract last year, meaning his current terms will expire this summer unless a new offer is made. Getty Out-of-contract Manchester United players Ander Herrera Contract expires: June 2018

Contains one-year extension? No



As with his compatriot Mata, Herrera's contract was automatically extended last year. The 29-year-old is currently on the fringes of Mourinho's squad.

Getty Out-of-contract Manchester United players Ashley Young Contract expires: June 2018

Contains one-year extension? No



Another whose terms were extended last year, Young's seniority and versatility stands him in good stead with Mourinho, even at 33-years-old. Getty Out-of-contract Manchester United players Antonio Valencia Contract expires: June 2018

Contains one-year extension? Yes



United's club captain came back from pre-season unfit and has underwhelmed thus far, potentially harming his chances of a renewal. Getty Out-of-contract Manchester United players Phil Jones Contract expires: June 2018

Contains one-year extension? Yes



Jones' long-standing injury problems continue to blight him and could finally convince United's decision-makers that his time at Old Trafford is up. Getty Out-of-contract Manchester United players Andreas Pereira Contract expires: June 2018

Contains one-year extension? Yes



Pereira started United's opening two fixtures before falling back to the fringes, where he appears set to stay. Getty Out-of-contract Manchester United players Matteo Darmian Contract expires: June 2018

Contains one-year extension? Yes



Darmian came close to returning to his native Italy during the summer but ultimately stayed on to provide cover in both full-back positions. A January move is not out of the question. Getty

Both Arsenal and City instead seem to have got lucky. It’s just remarkable how little time it took for perceptions to do a complete 180. It’s instead got to the sorry point where it’s impossible not to wonder why exactly United signed him, given last week’s injury may actually have spared him the ignominy of being dropped against his old club. There’s already the ignominy of having scored fewer Premier League goals in 2018 than Chris Smalling and Patrick van Aanholt. Jose Mourinho does not view Sanchez as a certain starter, and would not be against selling him.

So, did they just buy him because they could, and because - as is now all too reflective of United right now - he represented a bit of star glamour and the status of beating their rivals, rather than because they actually needed him?

For his part, Wenger is said to have always been surprised United even went for the Chilean. He apparently couldn’t see where Sanchez fitted in their team, especially given how Mourinho’s side have been playing. Put bluntly, the movement around him wasn’t anywhere near good enough to get the best out of him.

And so it has proved, as a team so painfully lacking in intensity have served to suppress the intensity of one of the most relentless players in the game. It’s just ended up with Sanchez running aimlessly and pointlessly in a flat team without an attacking structure.

Sanchez’s reactions to teammates have thereby often been a picture, but now feel desperate rather than demanding, in the way they were at Arsenal.

Sanchez now cuts a disconsolate figure (REUTERS)

Wenger would privately describe Sanchez as “super, super gifted … but incredibly difficult”. He adores the forward as a player, since at his best he was such a typical Wenger forward - creative, attack-minded, instinctive and so fast - that he was worth the trouble.

Sanchez has always been something of a “loner”, never willing to mix with other Chileans in London who would invite him to barbecues, but that has become more pronounced at United. After a long-term relationship ended, he now finds himself “pretty much alone in a massive house, with his dogs, and the rain”. United sources just say he looks “extremely unhappy”.

Other sources who know Sanchez and have worked with him readily concede he is “difficult”, but don’t think of any of this would be an issue in a winning team that had purpose. He would just be energised, in all senses, and maybe in a way that could carry him through the cumulative wear and tear for that bit longer.

There’s also the inescapable fact City would have offered all of what Wenger felt was missing from United, and a lot of movement around Sanchez to really maximise his quality.

He won’t ever get that move now and, in that sense, may never really get to star in a properly winning club team.

Other than Barcelona 2011-13, when he was very much a support act rather than the primary star he was always been envisaged as - not least by himself - Sanchez has never really played in such a side. It could almost be argued that, relative to his sensational quality, he has actually had one of those unlucky club careers where he has never had the opportunity to maximise that quality.

Moments of brilliance have been few and far between (PA)

One immediate counter-argument, however, is that his own choices and contracts haven’t helped him.

This is a problem he and United face now that Sanchez wants to leave. The Chilean is said to have a “mad, mad contract”. Some sources say it is up to £500,000 a week once all commissions are paid. Others say it is actually beyond that.

Since the nature of these situations mean the player and his camp aren’t going to accept that much of a drop-off, it means there are very few clubs that can afford him, and one of those that can - PSG - are no longer interested.

Internazionale have been broached, or maybe Real Madrid, “if they get desperate”, in January.

Sanchez's future remains unclear (AFP/Getty Images)

There is even talk United may have to subsidise any deal if they really want to get rid.

This also feeds into the questions about why they even made the purchase, and gave that contract, in the first place. The club apparently did think his image rights would be of great value in South America, but that gamble has not paid off.

It also isn’t completely unlikely that he finds some spark at United again. Were Mourinho to go in the summer, or the manager maybe make a change with Sanchez, he could be electrically recharged.