Alexis Sanchez merchandise on sale outside the Emirates on Saturday
It seemed Alexis Sanchez was destined to become a Manchester City player, but Manchester United had other ideas.
In signing a star player from a major rival, United's capture of Sanchez has some similarities with Carlos Tevez joining Manchester City following his departure from the Red Devils in 2009 - a move that prompted City to erect an advertising hoarding in Manchester welcoming the player to the city.
It has even more echoes of Robin van Persie's 2012 move from Emirates Stadium to United, where City were again an interested party. That deal became a title-defining transfer.
So how did Sanchez end up diverting from the blue side of Manchester to the red? How will he fit in at United? And where do Arsenal, who have received Henrikh Mkhitaryan as part of the deal, go from here?
How has Sanchez ended up at United?
BBC Sport's Simon Stone
Had Manchester City played their hand a bit earlier back in August, it would never have come to this.
Although their £60m bid for Sanchez on deadline day last summer matched Arsenal's valuation, it did not allow enough time for the Gunners to push through the transfer of France international Thomas Lemar from Monaco.
The Chilean stayed put. City waited, confident. United watched, and pounced.
The billboard used by Manchester City when they signed Carlos Tevez in July 2009
In fairness to Pep Guardiola and the Blues hierarchy, they knew the dressing room dynamic could be an issue if Sanchez arrived in mid-season. The huge salaries associated with buying a player like Sanchez made it a delicate job. The Chilean is about to earn more than Kevin de Bruyne will get when his current contract is upgraded.
With a Premier League title to be secured and realistic hopes retained of winning every trophy on offer, including the Champions League for the first time, City were unwilling to make such a commitment and unwilling to risk unsettling a group of players who have done so well for the first half of the season.
United, on high alert following Jose Mourinho's recent public pronouncement that £300m was not enough to reinvigorate the ailing squad he inherited, spotted their opportunity.
For them, the dressing room dynamic is a secondary concern to having a winning one.
Despite landing the EFL Cup and Europa League in his first season, Mourinho knows having a decent shot at winning a bigger trophy requires better players - and quite a few of them. Sanchez unquestionably fits the bill.
They asked the price, were told the agents' fees - and worked out a plan.
Sources close to the deal are adamant it could have been pushed through without the involvement of Henrikh Mkhitaryan. We will never know the truth of that.
But, in Mkhitaryan, United had an asset surplus to their own requirements that Arsenal wanted. City did not. In mid-season, it meant the club who really needed Sanchez got ahead of the club for whom he would just have been a handy addition.
After that, it was all about cash. If it all seems quite simplistic, that's because it is.
As United boss Jose Mourinho said after Liverpool had paid Southampton £75m for defender Virgil van Dijk. "If you want the player, you have to pay. It is as simple as that."
Big-name moves from Arsenal to ManchesterPlayerSold toFeeDateEmmanuel AdebayorManchester City£25mJuly 2009Kolo ToureManchester City£14mJuly 2009Gael ClichyManchester City£7mJuly 2011Samir NasriManchester City£25mAugust 2011Robin van PersieManchester United£25mAugust 2012Bacary SagnaManchester CityFreeJune 2014Has Jose put one over on Pep?
BBC Sport's chief football writer Phil McNulty
Mourinho has clearly signed a player Guardiola would have liked at Manchester City - but whether he has outflanked his long-time managerial adversary is another matter.
There remains the feeling that in a perfect world, away from the complex financial arrangements that accompany major deals, Sanchez would have preferred City rather than United, with the opportunity to work with Guardiola again after their time together at Barcelona.
If City had the financial desire to do this deal, you suspect Sanchez would have been at Etihad Stadium rather than Old Trafford.
Jose Mourinho's capture of Sanchez is more about his need for players than putting one over on his rival Pep Guardiola
The final judgement on whether Mourinho has pulled off a coup over Guardiola will ultimately be made where it always is - on the pitch and in results.
Mourinho and United have signed a world-class player, someone very highly regarded by Guardiola, and there is no doubt he has the capacity to have a huge impact at Old Trafford.
And, inevitably, this will be portrayed as a victory for United and Mourinho.
If, as he takes his place among Mourinho's attacking riches, he can push United closer to City - or even beyond them - in the near future, then a genuine victory can be claimed.
For now, however, rather than Mourinho somehow putting one over Guardiola, it simply looks like United were willing to offer more than City to get the transfer over the line.
Where will Sanchez fit in at United?
Former England winger and BBC Radio 5 live pundit Chris Waddle
Sanchez is so versatile - he can play left, he can play right and he can play down the middle as centre-forward, or as a number 10. He is an excellent signing for United.
You have got a player who can play in four positions, so where he is used might depend on the form of their other forward players, and also what Mourinho wants to do in certain games, because we know he likes to tinker with his team.
One thing United have probably been lacking, although Jesse Lingard has done very well at it, is supporting Romelu Lukaku and coming from a little bit deeper and getting goals.
Able to play anywhere across the front line, Alexis Sanchez can provided support for Romelu Lukaku from a number 10 role
That is the sort of role I could picture Sanchez playing in - around and behind Lukaku in a sort of free role as a number 10, ahead of Paul Pogba and Nemanja Matic.
The left side of United's attack is another position you could see for him - even though he is right-footed, he likes to play on the left and cut inside from there.
But Anthony Martial has come into a good bit of form and so has Lingard so, at the moment, you would probably say that the right side of their attack is where he is most likely to be used to start with.
It does not really matter, though. We know Sanchez can play pretty much anywhere across the front line, and we know how good he is because of what we have seen from him in an Arsenal shirt.
When you have got a talent like that you just want him to get on the ball, especially in the final third of the pitch.
I don't think you can really coach a player like him. Yes, you can get him to fill in areas when you lose the ball - he will fit into their system in that way - but, if he does join United, when they attack then basically they just have to let the lad off the leash.
Are Man City concerned at missing out?
Former England winger and BBC Radio 5 live pundit Chris Waddle
Sanchez would definitely have fitted in at City.
I am sure he would have wanted to go there had they matched United's offer but they have obviously decided this is not a deal for them.
They clearly wanted him because they have been chasing him for several years now and came very close to getting him last summer.
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I can understand why, because he is their sort of player and could have slotted into their team in several positions in the same way he would do at United.
He has the work ethic that Pep Guardiola wants because he likes to press - if you watched him at Arsenal, he was always hounding opposition players, chasing them and trying to get the ball back as quickly as possible.
At 29, he still has four or five more years in front of him and, even just looking at this season, then he would have strengthened City at a time when they are chasing four trophies.
With Gabriel Jesus injured since the start of the year, Sergio Aguero has been their only fit striker and Guardiola clearly wanted another option there.
City's interest in Sanchez has led to speculation about Aguero's future anyway because, although he scores lots of goals, there is a question mark over about whether he does what Guardiola likes to see from his players.
Aguero works harder now off the ball than he did, but does he press hard enough, or does he chase the ball enough for what Guardiola wants?
Sanchez certainly does that. Maybe City have got someone else in mind, because they need another striker.
Mkhitaryan - a breakdown of trust
BBC Sport's Simon Stone
Mkhitaryan exits Manchester United after 18 months leaving behind a gnawing feeling Old Trafford never saw the best of its first Armenian.
In July 2016, it all seemed so different.
Mkhitaryan's controversial agent Mino Raiola went on the offensive to persuade Borussia Dortmund into selling their talisman. It cost about £30m to make Mkhitaryan Mourinho's third signing.
United's fans were given a glimpse of what to expect with an eye-catching performance on the midfielder's debut, in a pre-season friendly at Wigan. Within two months, that early optimism had disappeared.
After three substitute appearances, Mkhitaryan started against Manchester City at Old Trafford. For 40 minutes, the hosts were ripped apart by their neighbours. Plenty in red were poor but it was Mkhitaryan who did not return for the second half. He did not start another Premier League game for three months.
And really, although there were moments where Mkhitaryan looked to have won over his boss - he scored in May's Europa League final victory over Ajax - he never properly recovered.
It has always felt he was operating under a shadow, knowing any mistake would be seized upon by a manager who had quickly lost faith.
Another dismal performance in another damaging defeat - at Chelsea on 5 November - set fire to Mkhitaryan's United future.
A breakdown of trust with Mourinho, reported by the BBC, could not be repaired.
Mkhitaryan started just one more Premier League game. In his final match, in the FA Cup against Derby, he seemed inhibited every time he touched the ball. When he was replaced at half-time on that night, it felt like an act of mercy.
On form, Mkhitaryan is swift, a confident mover with the ball at his feet, controlled in possession, neat in the passage of play. The ability is there. Maybe, now, the confidence is not.
Arsenal boss Arsene Wenger's challenge is to restore Mkhitaryan to what he used to be - because to those who have watched him in Manchester, the idea of Mkhitaryan being Sanchez's equal is preposterous.
Where does this leave Arsenal?
BBC Sport's David Ornstein
Arsenal would have sold Sanchez last summer had they managed to sign a replacement, which shows that privately they had already come to accept the prospect of life without the Chilean. His departure this month, therefore, was no surprise.
Disappointment at losing a fine player is offset by the fact that Sanchez underperformed in the first half of the season, had not been posting remarkable statistics for some time, was never particularly popular in the dressing room and became determined to leave.
Arsenal's gamble of rejecting Manchester City's £60m offer and letting the 29-year-old enter the final year of his contract, optimistic that he would shine on the pitch, backfired.
But in Mkhitaryan Arsenal have a player they have long admired and narrowly missed out on in 2016. The Armenian suits their style, is marginally younger than Sanchez, held greater contractual value than him and is happy to be at the Emirates.
This is a mess the Gunners should never have been in, though it would have been far worse if Sanchez had gone for nothing at the end of the campaign.
And if Mkhitaryan can contribute to a rebuilding job which the club hope will see them competing for the biggest honours again in the not too distant future, it may eventually prove to be a good deal.
Source: bbc.com