Ronaldo, 22, would be following in the footsteps of legends George Best, Bobby Charlton and Denis Law.
United boss Fergie said: "Ronaldo must have a real chance of winning. It would be fantastic for the boy.
"He is definitely one of the best players in the world - there is no question of that. He influences games for us, both as a playmaker and a goalscorer.
"His improvement can be measured two different ways - his decision-making is very good now as opposed to when he was a young kid - and his goalscoring has improved each year.
"He is already in double figures and we haven't yet reached December, which augurs well for the rest of the season.
"And his scoring record for Portugal is phenomenal. It is almost one in two games, which is an amazing record for a young player.
"I don't think he needs any more endorsements from me. I've said time and again that I think he is a marvellous player.
"He is providing his own endorsements now with his performances on the pitch."
Ronaldo's main competition will come from AC Milan's Brazilian ace Kaka and Barcelona's Argy Lionel Messi, who are also named alongside him on the shortlist for the FIFA World Player of the Year award.