Retiring shirt numbers is a rare occurrence in football, with teams often doing so in order to honour notable past players after they pass away.
The number six was retired by West Ham United in 2008 to pay respect to legendary English defender Bobby Moore 15 years after his death.
Meanwhile, Birmingham City made the unusual decision to retire the number 22 shirt in order to honour their young talent Jude Bellingham ahead of his transfer to Borussia Dortmund in 2020.
Advert
While it is less common than in club football, national teams have also retired shirt numbers to honour former players.
In 2001, the Argentinian national team retired the number 10 to honour Diego Maradona but were forced by FIFA to take it out of retirement less than a year later at the 2002 World Cup.
However, after the legacy-defining run in the 2022 Qatar World Cup, the President of the Argentinian FA announced that the number 10 jersey would once again be retired once Lionel Messi calls an end to his international career.
Last year, the Italian Football Association signed an agreement with the government to ban players from wearing the number 88 to combat anti-Semitism in Italian football.
Advert
The number 88 is seen by some as a reference to a German Nazi slogan, due to its links with the letter H.
Speaking about the ban, Italy’s interior Minister Matteo Piantedosi said: "It is an adequate and effective response to an intolerable prejudice that still too often manifests itself in our stadiums.
"Anti-Semitism must be strongly fought, together with everything that excludes, despises and discriminates against every human being, every social group, every minority.
"The declaration of intent signed is only the first step of a broader strategy that will result in a new document on preventing and combating all forms of racism and discrimination in sport."
Advert
In April, Adidas banned football fans from buying German football kits with the number 44.
This was done as, due to their font, the numbers resembled the letters SS, the abbreviation of Schutzstaffel - the name of the Nazi's security force.
Adidas responded to questions raised by historians and fans who questioned the resemblance, stating that it was unintentional and that they would be blocking all personalisation of German jerseys with this number while also redesigning the number 4 on all new kits.