Wayne Rooney will never be a secret weapon. There has been too much of everything that catches the eye: talent, fame, success, failure and scandal. But there is a role he is yet to play. Manchester United, at least, must see him as one of the few figures who could upset the characteristic poise of Pep Guardiola's Barcelona in Saturday's Champions League final at Wembley. As it is, Rooney lacks a moment quite like that in his career.