"The complete unit" - Sir Alex Ferguson was talked out of signing Ballon d'Or contender at Manchester United

Sir Alex Ferguson, two days before Christmas in 2010, took his seat to address the media ahead of a Boxing Day clash with Sunderland and confirmed that a changing of the guard was on its way at Manchester United.

Five-and-a-half years after swapping Fulham for Old Trafford for a reported fee of just £2million, Ferguson announced that veteran goalkeeper Edwin van der Sar was planning to retire at the end of the 2010/11 campaign. Considering the Dutchman had already celebrated his 40th birthday, it was not too great a surprise.

But when you remember that Van der Sar, just two months earlier, had quashed suggestions made by former United goalkeeping coach Eric Steele that he had already made the decision to retire come the end of the season, Ferguson's admission did make the unimaginable hit home. Although the former Ajax star had only been at United for just over half a decade, he was part of the furniture. He was a figure that you almost thought United would never be without.

Ferguson, speaking on December 23, 2010, said: "We are planning for this being his last season." The finish line for Van der Sar was in sight.

Confirmation of his impending retirement meant United had to start drawing up a succession plan to find a suitable replacement for the outgoing Dutchman, who is now 52. The goalkeeper had played a key role in United's continued success under Ferguson since arriving at the club and had created a lasting legacy, meaning whoever had the task of replacing him had both big shoes and gloves to fill.

Van der Sar was one of the best shot-stoppers of his generation. He was an outstanding character, too, meaning he enjoyed a trophy-laden career, featuring 11 major honours during his time at Old Trafford.

The task of replacing him was an enormous one. Not only did United have to find someone who could fill Van der Sar's vacated void and hit the ground running, but they also had to source someone who could come in and become the face of United's goalkeeping department for years to come.

At the time, although it was only just over ten years ago, transfer fees were not as crippling and as astronomical as they are today, meaning United had a good chance of sourcing an ideal successor for Van der Sar without breaking the bank. After several months of speculation, the Reds, who ended Van der Sar's final season of his career by winning the Premier League title - his fourth - and finishing as runners-up in the Champions League, turned to unfamiliar Atletico Madrid goalkeeper David de Gea as their ideal pick.

Ferguson, along with goalkeeping coach Steele, had been to watch De Gea in action for Atletico and decided that he was the man to succeed Van der Sar and become United's new No.1, bringing him to Old Trafford in June 2011 for £18.9million, which, at the time, made him the second most expensive goalkeeper of all-time behind Italian icon Gianluigi Buffon. De Gea, who has since gone on to make more than 500 appearances for United, had impressed Ferguson during his scouting trip and had ticked several boxes.

Ferguson, speaking in 2016, recalled: "Eric and I went out to watch him against Valencia away, and the things he'd [Steele] been speaking about – his agility, his confidence, his speed – were evident. And Eric had been building a relationship with his parents and was so adamant that I had to trust him – and I'm glad I did because he was right."

But things could have turned out very differently had Ferguson stuck to his guns and not listened to Steele, who joined United just weeks after joining Blackburn Rovers. That was because Ferguson, who nailed so many recruitment decisions over the years, had a different goalkeeper in mind to replace Van der Sar, who went by the name of Manuel Neuer.

The legendary German shot-stopper was on the books of Schalke at the time and was generating a lot of noise about his potential through his performances. United were pitted up against Schalke at the semi-final stage of the Champions League in the 2010/11 campaign, meaning Ferguson had the chance to analyse him up close and personal.

The Reds won the two-legged semi-final 6-1 on aggregate, meaning it probably did not do Neuer, who was 25 at the time, too many favours. But although he conceded six goals in two games against the Reds, Ferguson was intent on extracting the Germany international out of Schalke and bringing him to Old Trafford.

"Eric Steele had been scouting David de Gea for quite a while, but then Neuer came on the scene at Schalke," Ferguson continued. "And I think Schalke would've been happy if we'd have gone and taken him.

"So my problem was Eric because he was adamant that we must take De Gea. I said, 'But, Eric, the boy Neuer is the complete unit; he's mature, his physique is unbelievable', and he [Steele] says, 'Yes, but in three years time, De Gea will be better'. I said, 'That's a statement'."

It certainly was a statement. While there is no denying that De Gea has been an excellent servant for United over the past 11 years, winning countless individual awards and seven major honours, Neuer has redefined the parameters of modern goalkeeping over the past decade or so. Not only is he a strong and capable shot-stopper, he has also proven himself as the best sweeper keeper the world has ever had the privilege of witnessing.

He is a ball-playing goalkeeper that is prepared to take calculated risks with the ball at his feet, almost acting as though, at times, he is an 11th outfield player. He is quick in possession, highlighting his ability and awareness to read the game.

In many ways, he has become the professor of modern goalkeeping, with ball-playing goalkeepers and playing the ball out from the back becoming a more and more familiar sight in the modern game. He has perfected the art and is still showing no signs of stopping at the age of 36.

Whenever his time comes to retire, Neuer, who finished third in the Ballon d'Or in 2014, will go down as one of the greatest goalkeepers of all-time, joining the likes of Lev Yashin, Gordon Banks, Dino Zoff, Iker Casillas, Petr Cech and Buffon in an exclusive category. He is a global treasure, mostly because of the way he has rewritten the laws of goalkeeping and perfected the art of being a sweeper keeper.

Although it is very easy to say now, more than a decade on, you do have to wonder how Neuer's career would have developed had he have joined United. One thing, however, is for sure: Erik ten Hag would have loved him, given how he likes his goalkeepers to be confident and progressive on the ball.

After United had settled on De Gea, who is four years Neuer's junior, to succeed Van der Sar, the German was snapped up by Bayern Munich, whom he has played for ever since. It was obvious Ferguson was onto something, meaning you do have to wonder if the Scot ever had any regrets about not following his own initiative, instead of choosing to follow Steele's lead.