The 25-year-old had been heavily criticised by United supporters following a number of high-proflie mistakes last season.
However, he has become one of the club's most consistent performers this campaign, playing 38 games, and Ferguson thinks playing alongside Rio Ferdinand has been a huge help.
"I don't know what the fans thought but there were never any doubts in my mind about Evans," Ferguson told The Observer.
"He had a period of a few injuries but he has toughened up now, he's done a lot of work in the gymnasium and he's 24 years of age. He's been a top player for us this year.
"There is no doubt he has been helped playing alongside the experience of Rio and he is now arguably the best defender in the country."