Ferguson has concerns over whether Ferdinand's body can handle the extra workload.
"I need to speak to the (United) doctor because we prepare Rio Ferdinand in a certain way and there are certain treatments he has to go through.
"He has to make sure he is going to be OK in terms of the number of games he plays.
"We have been doing that for two years and it has worked.
"We have to look at all these things before Rio decides (if he joins up)."
If Ferdinand did not report it would be a minor embarrassment for Hodgson given his climbdown from previous statements that he has "moved on" from the Manchester United defender.
"The procedures have been the same all season which has given him fantastic performance levels when he's playing for us," said Ferguson.
"We have to consider that and Rio is considering that. And we'll see what the outcome of that is."
Is Fergie right to be worried about Rio's fitness? Give us your shout below...