The Leeds United managerial favourite has worked with the out of favour Newcastle United player before.
If they appoint the Spanish legend, Leeds will certainly be hoping he can bring similar success to the Reading boss.
Fernando Hierro was playing for Real Madrid at the time.
Leeds United are once again searching for a new manager after Garry Monk's departure.
West Ham United boss Sam Allardyce says Alex Song is one of his best ever signings.