Ferdinand knows the midfielder has played a key role in keeping the Red Devils flying high since the turn of the year.
He said: "He was out of the game for months and yet he's come straight back into top-level football and he's hardly looked out of place. At this stage of his career, that's phenomenal.
"It's not just the quality of his football that impresses me but the way he's adapted physically.
"Would we have been in the same position without him? It's impossible to say. It's great to have him back, though.
"There are a number of reasons why we've done well since the turn of the year and there's no doubt that one of them is Paul Scholes."