Arsenal legend Patrick Vieira has now claimed that a former Manchester United player was the toughest opponent he ever faced. Having played for Arsenal 405 times, Vieira also had extensive experience of appearing in the Serie A with Inter Milan, Juventus and AC Milan. Across his career, Vieira played in the Champions League 76 times, and the competition was the only one which eluded him in. But despite all that experience, and all those opponents faced, Vieira remembers his duels with Man United as the most intense. The rivalry between Arsene Wenger’s Arsenal and Sir Alex Ferguson’s United is …