Since the early days of football, team numbers on football shirts have existed to identify who’s who on the pitch at any given time, and to clear up who should be where.
In the traditional setup, the team numbers wouldn’t mean an awful lot, and simply went up as you looked at the team on the field: no.1 would be your goalkeeper, as you’d start from the back, and it would just go up from there, until you reached no.11
These days, however, there are no real rules as to which numbers mean what, or which one you can select if you play. Certain teams, however, have iconic numbers which they’ll always make a big deal about. It’s usually the centre-forwards – 9 & 10, although David Beckham’s number 7 at Manchester United is a very coveted title to inherit.
Players now see those certain numbers as prized posessions: Eden Hazard at Real Madrid is now the no.7 (inherting the number from Christiano Ronaldo), despite being the no.10 at Chelsea, and clubs will give their best players the most iconic numbers.
Some players though either don’t care much for it, or just pick a favourite number, which is perhaps why Liverpool’s right back Trent Alexander Arnold has stuck with no.66 for most of his adult career, and Aston Villa centre back Tyrone Mings currently owns no.40.