Comments made early this week by the ex-United boss in an interview prior to the release to his new book 'Leading', he said that he had only worked with four "world-class players" during his time as manager of Manchester United: Eric Cantona, Ryan Giggs, Paul Scholes and Cristiano Ronaldo.
Now a UN ambassador, David Beckham said that he agreed with Sir Alex in a recent interview with the BBC: "I played for the greatest manager of all time, for the amount of time that I did.
"I was lucky to play with the players that I did, and be successful with the club that I loved, and still love.
"I tend to agree with the manager that there are certain players that you can call world class, and thankfully I played with many of them."
However, when asked if he was himself a world-class player, the ex-England captain denied it and turned his attention to players he'd worked with.