"His performances are consistently at a high standard. The thing is, he's getting better.
"Being made England captain and taking the armband in some United games has given him a boost. This season he's probably proved he's the best defender in the world."
Despite his admiration for Ferdinand, Carrick revealed he voted for Cristiano Ronaldo as his Player of the Year.
He added: "I picked Ronny because he's scored a hatful of goals and so many were important.
"A winger getting more than 40 is hard to comprehend. He'll get praise from all angles and rightly so but Rio has been unbelievable and defenders often get overlooked.
"The backline as a whole has been a big part of that. In any other year he would have been named Player of the Year."