Former Manchester United star Juan Mata has revealed that one of Sir Alex Ferguson’s biggest rivals tried to sign him during his prolific career. Juan Mata is currently a free agent after his contract with Vissel Kobe expired in January and the Spaniard subsequently departed the J1 League club. The 36-year-old attacking midfielder was one of two major signings under former Manchester United boss David Moyes, who succeeded Sir Alex Ferguson. Mata arrived at Old Trafford in the 2014 January transfer window after United agreed to a £37.1m deal with Premier League side Chelsea. The former Spain in…