Ever since the introduction of squad numbers for players, certain numbers have come to be associated with certain positions and types of players.
The No. 10, for example, is usually a skilled playmaker, a creative pivot point for a team such as Diego Maradona or Lionel Messi. The No. 9 has come to mean an out-and-out centre-forward and the No. 1 is, of course, usually reserved for the goalkeeper.
The increased commercialisation of the sport has even seen individual players build brands around their squad numbers, with Cristiano Ronaldo's 'CR7' empire perhaps the best example of that phenomenon.