The ex-England captain will hang up his boots at the end of this season as the only Englishman to win titles in four different countries having enjoyed success with the Reds, Real Madrid, LA Galaxy and Paris St Germain. He also spent two loan spells with Preston North End and AC Milan.
And the boss, who will bow out of the game on Sunday, was quick to honour his former student when quizzed during Friday’s press conference at Carrington: "It’s catching fire - these retirements," Sir Alex told reporters.
"He’s had a great career, David, and it’s amazing how he has from every sort of different way reinvented himself. Going to America, many thought it was the end of his career but he came back played for England, Milan and PSG.
"The one thing he always had was fantastic stamina. As a young boy, he had the best stamina in the club. All the figures in terms of endurance that we used to do, he was always ahead of everyone else."