The reigning champions sealed a £37.1m deal for the Spaniard at the weekend, with one reporter quipping he was once known as the "Nicky Butt of Burgos".
Rob Dawson, a reporter for the Manchester Evening News, attended Mata's unveiling and wrote on his Twitter a dissimulated quote from the former Chelsea man suggesting why he had taken the number.
"Growing up in Spain I was known as the Nicky Butt of Burgos. I shall wear No.8," was the reporter's satirical take on the topic.
Mata, who completed a £37.1million deal from Chelsea to the Red Devils at the weekend, was widely tipped to become the latest in a string of famous faces to have the No.7 emblazoned on their shirt, with George Best, Bryan Robson, Eric Cantona, David Beckham and Cristiano Ronaldo among the most high-profile.
The decision to take No.8, though, particularly considering midfielder Anderson - who has just joined Fiorentina but only on loan - is registered as the No.8, is a surprising one.
It points towards an inevitable summer exit for the Brazilian but also reflects the club's appreciation of the Spaniard's talents, allowing him to pick whichever number he liked from the remaining vacancies.
Burgos is the city where Mata was born and brought up as a child and where his footballing skills were first honed, so the irony extends given Butt's reputation as an industrious, combative performer with Mata possessing slightly different hallmarks to that of the former United No.8.
Mata's silky style and technical qualities are exactly what United have sorely lacked so far this season, hence the big-money arrival, and serve to stand him in the same sort of company as Paul Scholes despite Butt's legendary status at Old Trafford.
Rejecting the opportunity of taking on the No.7 shirt suggested a player who did not want to place added pressure on himself, particularly when you consider the euphoric response he has received since his arrival epitomises how much he will be relied on to dig United out of a mess this season.
Antonio Valencia endured a tough time with the famous number on his back and subsequently swapped back to 25. Mata will surely be looking to emulate one of the No.8 shirt predecessor's achievements at the club having taken on his number to live up to the satirical "Butt of Burgos" tag.
Should Mata have gone for the No.7 shirt at Manchester United?
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