Van der Sar, who turned 40 this year, is expected to hang up his gloves at the end of this season in order to spend more time with his wife Annemarie, who suffered a severe brain haemorrhage last year.
Ferguson has finally admitted that the Dutch star will depart at the end of the season, and concedes that Van der Sar’s exit was inevitable.
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"I have come to accept this will be Edwin's last season," Ferguson said in The People.
"It's sad but the difficulty for a goalkeeper when he gets to 40 is something which happened with Peter Shilton.
"All of a sudden, because of age, Shilton's form just collapsed and I don't think Edwin would want that. He is such a proud man and it's going to be a big loss.
"We had a chat last season about how he saw his future and he explained to me his plans, and nothing has changed from then.
"It's difficult because he has his wife's health to consider after her illness.
"She is fine now and seems to be really good but she still has treatments to get in Holland, with physiotherapy and things like that. So for him to be here with us would be difficult."
The Red Devils have already finalised the signing of 26-year-old Danish Anders Lindegaard to replace their veteran keeper.
Atletico Madrid custodian David de Gea, Schalke’s Manuel Neuer and Maarten Stekelenburg of Ajax have also been dubbed as potential new arrivals at Old Trafford, but Ferguson insists that nothing is set in stone as of yet.
"We haven't finalised our thoughts on the goalkeeping situation," Ferguson added.
"Edwin has massive experience and you can't buy that, so it's a difficult one because he has been a great goalkeeper and will be hard to replace."
Since joining Manchester United from Fulham in 2005, the Dutch shot-stopper has made 168 league appearances, helping United secure three Premier League title triumphs in the process.
By Elliott Binks
