A 'one-club man' is a player who spends their entire senior career at one club. Ryan Giggs and Paul Scholes spent their entire careers at Manchester United. Carles Puyol spent his entire career at Barcelona. However, Josep Guardiola played for Barcelona B, then Barcelona first team, then had brief spells at Brescia, Roma, Dorados, and Dia. The claimed answer (Joseph Guardiola) is correct.