When Edwin van der Sar announced on Thursday his inevitable retirement from the game, it was quite rightly met with praise from many for his 20-plus years of service to top-level football.
The 40-year-old joined Manchester United in 2005 at a time of transition for the club, but what is undeniable is that the six years' service he provided and the willingness to give him 'one more season' demonstrates just how difficult top goalkeepers are to sufficiently replace.
In a team that has won just about everything there is to win, and then some, over Ferguson's 25 years and counting at Old Trafford, a key point of that success has been down to who regularly pulls on the gloves in the United goal.
The correlation between great achievements and a top-class consistent goalkeeper on the pitch is undeniable. You only have to look at the world's top teams to know that.
Whilst having magnificent playmakers, bullish defenders, attacking full-backs and prolific goalscorers at your aid, every great team needs to have a man consistently performing between the sticks to stay a major force and win trophies.
The likes of Real Madrid, Barcelona, Arsenal and Chelsea can all be made examples in this instance.
Iker Casillas is still the lynchpin and captain of Real's side, and even when they have a team capable of demolishing the opposition in front of him, he is the man they still depend on and why, even with the influx of magnificent players to enter the Bernabeu in the last 10 years, he remains the leader.
Arsenal's problems in goal since the reliable David Seaman hung up his gloves in 2003 are also well-publicised; the eccentric Jens Lehmann, error-prone Manuel Almunia and the raw Lukasz Fabianski have all tried, and failed, to reach the standards set by the moustachioed, pony-tailed shot-stopper nicknamed "Safe Hands" back in the 1990s.
Many may say that Chelsea's Petr Cech has never been the same since nearly receiving brain damage from Stephen Hunt's challenge back in 2006, but his very presence still makes the Blues a better side with him, rather than without him.
As for Barcelona - the best side in the world going forward they may be, but Victor Valdes is an unsung hero despite not being an automatic pick for the Spanish national team.
Had it not been for Casillas, he would be vying for a place with another fine goalkeeper in Liverpool's Pepe Reina for the No.1 jersey.
When United won the Champions League in 2008 on penalties against Chelsea thanks to Van der Sar's heroics in saving Nicolas Anelka's spot-kick, Ferguson hailed the Dutchman for solving one of the biggest dilemmas he ever had to face in his time at the club - replacing the Great Dane Peter Schmeichel.
"If you recognise one big change in Manchester United in the last few years it's in the goalkeeping," he said prior to that final in Moscow.
"We found it hard to replace Schmeichel but his (Van der Sar's) calmness, composure, his presence is phenomenal. He's a vital, vital player."
Vital is not a word used by Ferguson for many players, so for him to say that means he really is, and will be sorely missed.
For if you take Cech, Reina, Valdes, Casillas, Julio Cesar from Inter, or even a long-serving first-choice goalkeeper from any squad, it's almost a guarantee that you'll have to wait a while to properly replace them.
This was the problem Ferguson faced upon Schmeichel's departure.
Mark Bosnich, Tim Howard, Massimo Taibi and Roy Carroll were all decent enough players, as proved by Howard's time at Everton since, but the pressure that comes with playing for Manchester United needs a character of more than just agility and good reflexes to succeed.
When French World Cup winner Fabien Barthez joined United from Monaco in 2000, many thought Ferguson had found the replacement he really needed.
A world-class shot-stopper with European pedigree and a strong character he may have been, but his tendency to wilt at vital moments and display his eccentricity on too many occasions was too much of a weakness for the team to carry.
The bald-headed Barthez did not last long and, despite winning two titles with United, he was shipped off to Marseille three-and-a-half years later, clearly not being the answer to the problem.
Ferguson got the man he wanted in Van der Sar. A tall, experienced, agile and commanding presence who found his best form at Fulham after a spell with Juventus in the late 90s, giving every justification as to why he was so highly regarded at Ajax.
Like every goalkeeper, Van der Sar has made mistakes, but it is his ability to pick himself up and move on to the next great save or vital intervention in no time that has put him alongside Schmeichel in the hall of fame.
So who will replace the Dutch giant? Ferguson may feel he has the new Schmeichel in Anders Lindegaard, who is Denmark's new hope in goal, and at 26 does represent the kind of similar success story Schmeichel enjoyed in the North West.
But the desire to plump for someone with the know-how of coping under intense pressure must be there for the wily old Scot.
After all, whilst he's had a very good season at Birmingham, Ben Foster looked like he wanted the ground to swallow him up at times when representing United.
It is this headache that is probably going to gnaw away at Ferguson from now until the start of next season, especially with the Red Devils not as frivolous in the market as they used to be.
He is also a man who doesn't like making the same mistake twice, and will know that much can hinge on his developing team having a man between the sticks to guide young defenders Chris Smalling and Jonny Evans through tough situations.
David de Gea looks like the Van der Sar incarnate of the future, and is yet another Spanish keeper attracting attention after some fantastic performances for Atletico Madrid, but at the tender age of 20, he is probably not the answer just yet.
The likes of Russian captain Igor Akinfeev, Van der Sar's Holland successor Maarten Stekelenburg, Germany's Manuel Neuer and even an audacious move down the M62 for Reina have all been linked as possible moves.
However you wouldn't bet against Fergie going down the road to Manchester City and seeing how much Shay Given might be worth.
The Irish goalkeeper has tasted hardly any football this season thanks to the rise of Joe Hart, but there is little doubt he still has the class and the experience to retrace the steps of Carlos Tevez to go the other way to the red half of Manchester and take the No.1 jersey.
Indeed, Van der Sar joined the club at the same age as Given, and obviously proved an enormous success, with a fourth Premier League medal a very possible send-off.
So Ferguson has some thinking to do, and it is a fitting tribute to the service Van der Sar has given the club over the past six years and the legacy he leaves. But whatever the case, the current league leaders might have just as much difficulty replacing the big Dutchman as they did the Great Dane.
Who should be Edwin van der Sar's long-term replacement?