But Fergie says: "(Bryan) Robson was an incredible presence in the dressing room
"He was loved by the players and tactically very astute.
"(Roy) Keane was a driving force, but neither were the best footballers. They had unbelievable qualities that made them great players, but the great players we've had in terms of real quality, you have to look at Eric Cantona, Ryan Giggs and Cristiano Ronaldo, Wayne Rooney and Paul Scholes.
"But to try to say who was the best of them all is very difficult.
"No player has run up and down the touchline in the Premier League as long as Giggs. He's done it since it started.
"His consistency and quality mark him down as the best player ever in the Premier League. He is an incredible player."