Ferdinand believes the pressure on Rashford has pushed him towards leaving Old Trafford.
Rashford revealed in December that he is ready for a new challenge after nine years at his boyhood club, with Barcelona, Borussia Dortmund, and Napoli showing interest.
Ferdinand told The Mail: “Manchester United, also people around Marcus, need to make sure that he leaves in the best tact mentally as well as physically. Mentally more importantly because I think he's been over-scrutinised for a few years now.
“But that also comes in the territory of being a Manchester United player. And when you're held up as one of the faces of the club then that is part and parcel unfortunately of being at Man United.
“I think it's always easy for everyone else to assume and think what he should do but I think only Marcus and his team know what are the benefits of staying in Manchester or at United.
“What's going to be beneficial for him leaving? But then the question is where do you go? So there are a lot of questions that need answering but only he is going to be able to do that.
“The only thing I would be advising him on — if I was his advisor — is he is never going to be 100 per cent certain that the decision he makes at this crossroads is right. He is going to do something — whether he goes or stays — and when he makes that decision he will still not be 100 per cent sure.”