The Red Devils manager feels the right back is improving all the time and has everything required to become the complete player.
Currently without Phil Jones and Chris Smalling due to injury, and with twin brother Fabio sent out on loan at QPR, Rafael is the only right-sided fullback available to United at the moment and has staked his claim for a first-team place with a level of consistency which had been lacking in previous seasons.
"He is maturing and learning all the time," Ferguson told Sky Sports. "Rafael has all the ingredients of a great player. He is blessed with great enthusiasm, skill and speed. He was quite impulsive and tended to over-commit himself. We have gone over it a few times but, bit by bit, it is all coming together and he was easily our best player Saturday."
Rafael himself also revealed that his maturity has improved greatly from last season - a time in which he was at fault for sloppy goals conceded against Everton and Athletic Bilbao, as United finished the season without any silverware.
"I do think they look at me differently now," Rafael said. "The way I play for United has changed a little bit and I have scored some goals as well. But mature is the word. I always want the ball. Now I read the game more and know what the opposing player is going to do."
The 22 year-old also emphasized the importance of playing for his country, and the wave of excitement and expectation that has swept over Brazil.
"It is a big time for me. The World Cup is the big competition for Brazil and all the fans expect us to win. I am really looking forward to being there," Rafael said.