But his performances have prompted a double-your-money deal from United's board worth £50,000 a week.
Ferguson said: "The quality Nemanja has is that he is so brave. He is a great defender and he's a real threat up front as well.
"He can play too but, importantly, he doesn't mess about at the back."
Vidic scored four goals last season and Ferguson believes he can improve on that this season.
Fergie added: "He is prepared to put his head in and that always makes him a threat up front. He can easily get 10 this season."
Vidic, 26 next month, insisted: "I plan to score lots of goals this year. If they come off my head, my feet or stomach, I don't mind. I want to help the team win more matches."