Manchester United manager Sir Alex Ferguson has described David Beckham as an "amazing person" and says his ability to reinvent himself is "absolutely incredible".
Paris St-Germain midfielder Beckham, 38, is to retire from football at the end of the season.
He played for 11 years under Ferguson at United between 1992 - 2003.
"You talk about longevity and in many ways reinventing himself, it has been absolutely incredible," Ferguson told the BBC on Friday.
When he went to America there wasn't a person in this place who really thought he could have a career," Ferguson added about Beckham's move to LA Galaxy in 2007.
"Yet he went on and still played for his country, he played for AC Milan in European ties and he played for PSG in European ties, and I don't think anyone could have imagined that."
Ferguson signed Beckham at the age of 11 in 1991 and he graduated from the 'Class of 92' along with Ryan Giggs, Paul Scholes, Gary Neville and Nicky Butt.
Beckham made almost 400 appearances under Ferguson, winning six Premier League titles, a Champions League medal and two FA Cups.
Move to Real Madrid
But the pair had a fall-out in 2003 following an FA Cup defeat by Arsenal when Ferguson kicked a boot in the Manchester United dressing room which hit Beckham in the face.
Later that year, Beckham moved to Real Madrid for £24.5 million.
The former England captain joined LA Galaxy four years later. In winning the Ligue 1 title with PSG in France last week, Beckham became the first English player to win top league titles in four different countries.
"The one thing he always had was unbelievable stamina as a kid. He had the best stamina in the club,'' Ferguson told the BBC.
"He could run all day, and that has allowed him to stay in the game at that kind of level, playing for his country in his mid 30s. Coming from American football to do that is quite amazing, and he is an amazing person.
"I think he's picked the right time (to retire). He's won the league again with PSG and he is exactly the same as me, he has plenty of things to do.''
