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.
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 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 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."
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