Ferdinand, who turns 33 on Monday, has increasingly struggled with injury problems in recent seasons - making it difficult for him to appear regularly for United. He was also left out of the first team in favour of Jonny Evans for the trip to Everton at the weekend, despite both playing a part in the recent 6-1 hammering at the hands of Manchester City.
Ferdinand's partnership with Nemanja Vidic has long been considered among football's very best but, with both Chris Smalling and Phil Jones pushing for regular first team football since joining the club, Ferguson has acknowledged that the man he signed from Leeds United for £30 million in 2002 is no longer one of the first names on the team sheet.
"I explained to Rio that, simply, we have two young centre halves coming through," Ferguson said, ahead of United's Champions League game against Otelul Galati on Wednesday. "I'm really happy to have the four of them and I hope to keep the four of them for a long time, but Rio is obviously 33 now and he's obviously lost the yard of pace he had five years ago."
While Ferdinand will no longer be an automatic selection for United's most important games, Ferguson expects him to remain a valuable player for the club - although he will need to adapt his game as a result of his physical limitations.
"That doesn't mean to say he can't play the game in a different way - where he used to rely on his place he doesn't do that now, he can't do that now. That's obvious," Ferguson added.
"We've all faced that decisive moment in our careers where you realise you have to change your game. I did it myself as a player when I lost that real sharpness, and Rio will do the same and he'll be fine."