Giggs, who made his debut for the club 20 years ago in 1991, has already signed a new contract for next season which will take him through his 38th birthday. But time shows no sign of catching up with a player who has already made a record 873 appearances, before the trip to Arsenal, for the club.
Last month Burnley defender Graham Alexander joined Tony Ford as the only outfield players to pass 1000 appearances. If Giggs plays on he will join them, but Alexander and Ford played their football in the lower divisions and for Giggs to complete the feat playing all his matches in top-flight football would be an astounding achievement.
Sir Alex told the Sunday Mirror: "He's been unbelievable, fantastic. I don't know how he does it. He's 37 years old and still looks as if he's got four or five years left in him.
"Of course, when you get older it can hit you quickly. You never know. But what he's doing at the moment is quite amazing.
"Ryan has never had any weight problems. He's also got great balance. You never see him get whacked because his balance is so good."
Ferguson also revealed he is still hoping to persuade Paul Scholes to play on for another season. Unlike Giggs, Scholes has so far not committed to another 12 months with United.
He added: "I've had a few chats with Paul, encouraging him to stay on. We'll see."