Sir Alex Ferguson: I only ever had four world-class players at Manchester United

Eric Cantona (left) is one of only four world-class players Sir Alex Ferguson claims to have worked with at Manchester United

Sir Alex Ferguson has insisted he only ever had four truly world-class players at Manchester United - and neither David Beckham nor Roy Keane are among them.

The former United boss of 26 years, who won 13 Premier League trophies, believes that only Ryan Giggs, Paul Scholes, Eric Cantona and Cristiano Ronaldo deserve that title.

"They made the difference and the evidence is there," Ferguson said.

"When we brought Eric 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. 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.

"And of course Ronaldo was just a complete genius of a player."

Ferguson was speaking at the launch of his new book 'Leading', in which he divulges a string of revelations about the search for his successor, United's transfer dealings, his own wage demands and relationships with other clubs.

In the book, Ferguson reveals…

David Moyes was not United's first choice as his successor. The club considered Pep Guardiola , Jose Mourinho , Carlo Ancelotti , Jurgen Klopp and Louis van Gaal before appointing him.

was not United's first choice as his successor. The club considered , , , and before appointing him. Giggs has the potential to become a 'top manager' but he would never have asked a player to fill his shoes.

has the potential to become a 'top manager' but he would never have asked a player to fill his shoes. He insisted on being paid at least as much as Wayne Rooney when the striker was given a dramatic wage increase in 2010, believing 'no player should be paid more than the manager'.

when the striker was given a dramatic wage increase in 2010, believing 'no player should be paid more than the manager'. The breadth of Ronaldo 's vanity was such that his team-mates would "throw jock straps and socks at him" while he posed in the mirror.

's vanity was such that his team-mates would "throw jock straps and socks at him" while he posed in the mirror. It was a "costly error" to baulk at Atletico Madrid 's £35m asking price for Sergio Aguero , who signed for Manchester City instead in 2011.

's £35m asking price for , who signed for Manchester City instead in 2011. Dealing with Tottenham chairman Daniel Levy when signing Dimitar Berbatov was "more painful than my hip replacement'.

chairman when signing was "more painful than my hip replacement'. He turned down the chance to manage Inter Milan and had interviews to manage Barcelona and Wolves while he was manager of Aberdeen.

Ferguson told Sky Sports News HQ in an exclusive interview on Monday that he believes Van Gaal has the pedigree to be a success at Manchester United.

The 73-year-old also divulged that he wanted to sign Arsenal's Tony Adams and admired Sky Sports' football expert Jamie Carragher while he was Liverpool and Gianfranco Zola at Chelsea.

You can watch the entire 30-minute Sir Alex Ferguson interview On Demand now