Sir Alex Ferguson believes that he only managed four truly world-class players throughout his historic tenure in charge of Manchester United. The Scot has also revealed that Pep Guardiola was the top choice to take over at Old Trafford upon his retirement in 2013.

Throughout an illustrious 27-year reign in the job, Ferguson garnered a formidable reputation and established himself as one of the greatest managers in football history by winning no fewer than 13 Premier League titles as well as five FA Cups, four League Cups and two Champions League crowns. Such overwhelming success could obviously never have been achieved without the benefit of a consistently strong playing squad, yet it appears that only a select few, not including the likes of David Beckham, Roy Keane or Peter Schmeichel, were ever deemed worthy of comparison with the very best talent from overseas.

"If you read the papers or listen to the television commentators, we seem to be awash with 'world-class' footballers," the 73 year old wrote in his new book Leading, which is co-authored by Sir Michael Moritz, as quoted by the Daily Mail. "In my book there are only two world-class players playing today: Lionel Messi and Cristiano Ronaldo.

"I don't mean to demean or criticise any of the great or very good footballers who played for me during my 27-year career at United, but there were only four who were world class: [Eric] Cantona, [Ryan] Giggs, Ronaldo and [Paul] Scholes. And of the four Cristiano was like an ornament on the top of a Christmas tree."

Among several other intriguing topics covered in Ferguson's latest publication includes the process to determine the identity of his successor. David Moyes was eventually appointed to the position after proving his mettle during an 11-year stint with Premier League rivals Everton, yet was relieved of his duties after only 10 months with United languishing seventh despite having won the title the previous year.

While many at the time of his unveiling claimed that Moyes had been Ferguson's first choice to succeed him, it seems that former Barcelona favourite Guardiola was the main target prior to his decision to end his self-imposed sabbatical and take over the reins at Bundesliga giants Bayern Munich. Jose Mourinho, Jurgen Klopp, Carlo Ancelotti and even current boss Louis van Gaal were among the other high-profile candidates ruled out of the running at an early stage.

"I had dinner with Pep Guardiola in New York in 2012, but couldn't make him any direct proposal because retirement was not on my agenda at that point," Ferguson said according to The Telegraph. "He had already won an enviable number of trophies with Barcelona... and I admired him greatly. I asked Pep to phone me before he accepted an offer from another club, but he didn't and wound up joining Bayern Munich in July 2013."