The traditional 1 – 11 numbers have been worn on occasions by English clubs since their respective leagues introduced squad numbers . Premier League clubs often used the traditional squad numbering system when competing in domestic or European cups , often when their opponents still made use of the traditional squad numbering system . This included Manchester United 's Premier League clash with Manchester City at Old Trafford on 10 February 2008 , when 1950s style kits were worn as part of the Munich air disaster 's 50th anniversary commemorations
Munich air disaster
Munich air disaster
Squad number (association football)