Group numbers really mean nothing and are only used to differentiate between players, right? If only it were really true.Some clubs 'team numbers have become iconic over the years, with Manchester United's number seven, Newcastle's number nine and Arsenal's number ten in particular weighing their occupants for several years after the previous owners' success.Emile Smith Rowe is Arsenal's new number ten / Shaun Botterill / Getty ImagesMesut Ozil, Jack Wilshere and, erm, William Gallas have all struggled to live up to the…