Sir Alex Ferguson says just one 'unbelievable' player is 'guaranteed' to make his all-time Man Utd XI

Sir Alex Ferguson has revealed the one player that is guaranteed a place in his all-time Manchester United starting eleven and it's not Cristiano Ronaldo.

Ferguson took over the Old Trafford back in 1986 and went on to become one of the best managers in football history after a 26-year spell as United boss.

During his time as manager, Ferguson led the Red Devils to 13 Premier League titles, five FA Cups, four League Cups and two Champions League titles.

Ferguson was also responsible for bringing through some of the best players to ever play for the club, including the likes of Roy Keane, David Beckham, Wayne Rooney and Cristiano Ronaldo.

When Sir Alex announced he would be retiring from management in 2013, he was asked to name his best-ever United starting XI.

He told the Sunday World: “People ask you: ‘Who is your best Man United team?’ and it’s absolutely impossible.

“It is absolutely impossible. You look at the strikers I had, going back to [Brian] McClair, [Mark] Hughes, [Andy] Cole, Cantona, [Ruud] van Nistelrooy, [Louis] Saha, Ole Gunnar Solskjaer, [Dwight] Yorke, Teddy Sheringham.

“Then to the present players -- Wayne Rooney, [Robin] van Persie, Chicharito [Javier Hernandez]. How do you pick out of that? Cantona and somebody else maybe?”

Ferguson added: “The midfield was probably a bit easier because you have [Roy] Keane, [Bryan] Robson and Scholes -- they were fantastic players -- and [David] Beckham, Ronaldo and [Ryan] Giggs.”

In his autobiography, Ferguson revealed Denis Irwin is the only guaranteed name in his best-ever starting XI.

He said: “Honestly, I would say Denis Irwin would be the one certainty to get in the team. I called him an eight out of 10.

Denis Irwin- Getty

“At Highbury in one game, he had a bad pass back in the last minute and [Dennis] Bergkamp came in and scored.”

The Scotsman continued: “After the game, the press said: ‘You must be disappointed in that pass back.’ I said: ‘Well, one mistake in 10 years isn‘t bad.’ He was an unbelievable player.”