Reports from The Independent and Daily Mail this week both state that Sanchez has been offered/will take the jersey made famous by the likes of George Best, Bryan Robson, Eric Cantona, David Beckham and Cristiano Ronaldo.
It was certainly the obvious and expected choice for a player who has worn number seven for Arsenal for the last 18 months after inheriting it from Tomas Rosicky - prior to that the ex-Barcelona forward had worn number 17 for the Gunners.
Sanchez also dons seven for Chile at international level, wearing it at every major international tournament he has played for his country, dating back to the 2010 World Cup.
Given the legendary status of many of its previous wearers, there is a weight of expectation that comes with the number seven shirt at United.
It has remained vacant for a year, with flop Memphis Depay was the last player to wear it. Prior to the confident Dutchman taking it in 2015, the shirt had been worn by Angel Di Maria. Antonio Valencia also had it for a single season in 2012/13 before switching back to his old 25 shirt.
The only other player to wear it since Ronaldo was Michael Owen between 2009 and 2012.
While looking likely, Sanchez's arrival at United still seems to hinge on Henrikh Mkhitaryan agreeing personal terms with Arsenal in the proposed player exchange deal.
What number the Armenian could wear at the Gunners is less clear. He has worn number 22 for most of his career - at United, Shakhtar Donetsk, Metalurh Donetsk and first club Punyik. But it is already occupied at the Emirates Stadium by emerging youngster Jeff Reine-Adelaide.
His number at Borussia Dortmund was 10, again already taken at Arsenal, by Jack Wilshere. His usual number at international level is 18, currently worn by Nacho Monreal for Arsenal.
Not just replacing Sanchez on the pitch, Mkhitaryan could take the Chilean's old shirt, number seven. Other possible shirts are 14, set to be imminently available as a result of Theo Walcott's virtually complete move to Everton, and 15.