Ryan Giggs believes Sir Alex Ferguson could carry on for another five years at least as Manchester United manager and remain at the helm well into his seventies.
The club's record appearance holder says his veteran boss, who turned 69 last month, has an enduring passion for the game.
In an interview with Sky TV magazine, Giggs said: "I really do not see him (Ferguson) finishing any time soon, he will go on, at least another five years."
He added: "His desire gets stronger. After a Champions League game we can get back at 3.30am and then a few hours later he will be the first in at the training ground.
"Earlier in the season we had a virus at the club. He got it himself and was dying during the week, really sick, but come the day of the game, he was there in the dug-out. He just loves the challenge."
Giggs intends to follow Ferguson and become a manager somewhere. He is currently taking his A coaching badge.
He added: "I want to remain in football so I can continue to do something I have done since school. If I have a day off I am bored.
"I hope I can be a good manager, I like helping players and improving them. But the life expectancy of a manager is just 18 months, so you do not get long."