The former Liverpool forward has made just one start in four Premier League games for United since arriving at Old Trafford from Newcastle, but he has already scored twice after coming on as a substitute.
"Michael was only on for something like 17 minutes," said Ferguson.
"He was the best man to be on there when the game is going to be in their penalty box. There is no-one better at taking chances.
"His positional play, first touch and finish were absolutely superb. World class."
Sunday's derby had been preceded by some verbal jousting between Ferguson and his City boss Mark Hughes, and the Scot was quick to remind his managerial counterpart that United had secured local bragging rights - for the time being at least.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.