The 31-year-old has endured a dismal time with injuries for almost two years now.
Ferdinand is set to begin his latest comeback at Everton tomorrow after battling to overcome the knee injury he suffered in a freak collision with Emile Heskey on the first day of World Cup training which prevented him from playing any part in South Africa.
In the intervening period, England suffered a dismal campaign in South Africa and then emerged as a far stronger force, winning their most recent Euro 2012 qualifiers, beating Bulgaria and Switzerland whilst scoring seven goals in the process and conceding only one.
That has brought Ferdinand's position in Fabio Capello's squad into question, with even some of those who feel the Manchester United defender should be picked believing it would be better if Steven Gerrard took over the captain's armband.
Yet Ferguson does not feel it is a matter for debate.
"Rio had a nightmare season last year so the main incentive for him is to stay fit," said the United boss.
"If he stays fit then he will be picked for England because he is the best centre-back."
Ferdinand did ask to play in last night's reserve team encounter with Stockport, only for his manager to rule that move out on the grounds that he would need the former Leeds skipper at Goodison Park.
"I can only go on his training performances," he said.
"Our training is not easy. The whole thing is quite intense.
"He has done really well. I could easily have played him in the reserves but I didn't see any point in playing him for an hour if I am thinking of using him tomorrow."
Ferdinand's performances should be sharpened up by the knowledge there are others after his place.
Nemanja Vidic has just signed a new four-year contract, Jonny Evans has proved himself more than just a capable deputy while England Under-21 star Chris Smalling is desperate for the chance to prove himself.
"We have some terrific centre-backs here," said Ferguson.
"Smalling has improved fantastically over the last few weeks. His performances for the England Under-21 team have earmarked him down as a really top young player.
"Then there is Evans and Vidic.
"It is terrific I have that kind of competition because last season three of those players were always injured."