Questions are being raised over Amorim's appointment with United now sitting in 14th place on the Premier League table.
But Ferdinand said on his podcast: "You look at him and you think, 'He always seems pretty confident in the long term, he's not going to change his ideas in the short term'. And I totally agree.
"To change and go back to what they were doing before… they weren't winning. So why go back to what suits the players?
"We can't expect Ruben Amorim to go back to the way Manchester United used to play and try to steady the ship. Because it wasn't a stable ship anyway."
He also said: "One of the key points in this system is the physicality. (Christian) Eriksen and Casemiro are probably the weak links - which doesn't help - but I still say that if they could train and Ruben Amorim could implement his ideas, they wouldn't look so 'out of place'. So I don't think we should just say: 'Let's put two more mobile players and everything will improve'. I think we will still have the same problems."