Legendary manager Sir Alex Ferguson spent 26 years in the Old Trafford hot-seat before retiring in 2013 with 13 Premier League titles.

Upon joining, the Scottish manager insisted that his greatest challenge was to "knock Liverpool off their f***ing perch".

Liverpool - without a title win since 1989 - have won 18 league titles in their illustrious history but Manchester United claimed their 19th in 2011.

Ferguson made some incredible signings during his time in Manchester and picked out his best four in 2012.

However, he did famously also bring in the likes of Eric Djemba-Djemba, Bebe, Kleberson, Dong Fangzhuo and Massimo Taibi.

You can't win 'em all.

Fergie's four greatest signings

"Was Cantona your best ever signing?"

"It's a good question," replied Sir Alex Ferguson, as per the Manchester United website. "Well, in terms of value, Eric was around £1million, Peter Schmeichel was £500,000, Brian McClair was £800,000 – they were all fantastic. Paul Ince was a million and a half and we sold him for eight, Ruud van Nistelrooy was value in terms of selling him, and the players we produced ourselves after signing them as schoolboys, they’re total profit.

"Then you have Cristiano Ronaldo, £12m to £80m! If you’re talking about the best players in terms of value, then Schmeichel, Cantona, McClair, Ronaldo – unbelievable.

"But to analyse the signing as it was without talking about money, Eric certainly brought a great confidence to the team, there’s no doubt about that.

"He brought an arrogance, and for him personally it was as if he had come to the place he always wanted to be. You could tell he would fit in straight away. He came on for the first time as a substitute against Man City, for Giggs. But when he came on I always remember his first pass, just a ten-yard simple pass – it was just genius. You knew then that he was fitting in."

Cantona joined the club from Leeds United in 1992 and won four league titles in five seasons in Manchester.

Schmeichel signed from Brondby in 1991 and racked up five league titles and a Champions League winners medal during his eight-year stay at Old Trafford.

McClair was an early Ferguson buy, spending 11 years as a Manchester United player and winning four Premier League titles following his move from Celtic.

Ronaldo joined as a teenager from Sporting CP and developed into one of the greatest players of all-time during his six-year stay in Manchester.

Now 32, Real Madrid's Portuguese superstar won three Premier League titles and a Champions League during his time under Fergie.