But that is exactly what he did in 1995 after a cheeky request from one of his players.
Sir Alex, more affectionally known as ‘Fergie’, was well-known for taking a no-nonsense approach in his time at Manchester United.
The Scot was a pioneer in what is now known as the ‘hairdryer treatment’ as he came to blows with several of his players.
His most famous bust-up came when he kicked a football boot at David Beckham in frustration, causing the global superstar to have stitches above his eye.
But the 77-year-old seemed a little calmer after a disagreement earlier on in his reign.
One of the most important transfers of his United career, Ferguson signed Andy Cole from Newcastle in 1995 for a record British deal worth £7m.
He immediately gave the striker the No. 9 shirt, leaving Brian McClair numberless.
Ferguson broke the news to him, telling him he could have any vacant number he wanted.
According to The Athletic , a mischievous McClair simply told his fellow countryman: “Okay, 69. Thank you.”
Of course, Ferguson was never going to let the player have that on the back of his shirt.
The debate lasted a good few days though before the pair came to an agreement, McClair settling on No. 13.
Anthony Martial has taken up the number for this season, joining a list of football legends to wear it – though their fortunes at Old Trafford certainly differ.
Romelu Lukaku was the man who left it vacant for Martial, who had replaced Swedish hero Zlatan Ibrahimovic.
Battling midfielders Paul Scholes and Roy Keane have both also occupied it in the past, as well as Old Trafford favourite Sir Bobby Charlton.