Sir Alex Ferguson says he managed only 4 world-class players at Manchester United

Manchester United's legendary manager, Sir Alex Ferguson, has worked with some of the biggest stars in the game, but his personal list of world-class footballers is only four players long - and Wayne Rooney isn't one of them.

The Scottish gaffer revealed in his latest book, "Leading," that while he has overseen the careers of some of the greats, he only considers Eric Cantona, Cristiano Ronaldo, Ryan Giggs, and Paul Scholes as his world-class pupils.

"They made the difference and the evidence is there," Ferguson told the BBC, as quoted by ESPN. "When we brought (Cantona) in we won the league that season - it was his mere presence and his ability to make and score goals.

"The younger breed like Ryan and Scholes were just fantastic players and the thing about those two was longevity," he continued. "Are there players who have played right through the whole of the Premier League and performed at the level they have? There are none, absolutely none."

Of the four, Ronaldo is, perhaps, his greatest understudy. The Real Madrid man has become a record-shattering star in the Spanish capital.

"Of course, Ronaldo was just a complete genius of a player," Ferguson said. And while he didn't necessarily deny that Manchester United produced other great talents, he added that those four players "elevated themselves above that (level)."

That list of great talents includes the likes of Ruud van Nistelrooy, Roy Keane, and David Beckham.