Fergie said: "Rio has been captain with Gary Neville injured and Ryan Giggs unavailable.
"And obviously as Ryan gets older Rio is the natural successor - that is his destiny.
"His experience has added to his many abilities. He is one of the most natural footballers in England.
"For a defender, he is so quick and mobile and technically gifted.
"His performance in Barcelona was absolutely superb. He and Wes Brown were fantastic."