Giggs will make his 700th appearance against Liverpool today.
Fergie said: “I think it will be increasingly difficult these days for a top player to stay at one club.
“Yet we have Gary Neville and Paul Scholes as well as Ryan who quite possibly could do it, which is phenomenal for Manchester United.
“In the case of Ryan he is an exceptional person. He has prepared the right way to be a top footballer, his behaviour patterns and how he looked after himself all the time have always been good.
“And also he has this incredible talent that has never left him and never waned in a 16-year period, it’s phenomenal.”