Ferguson kept faith with goalkeeper De Gea when he experienced early teething troubles following a much-trumpeted £18million summer move from Atletico Madrid.
However, when the Spain Under-21 star cost United more points against Blackburn on New Year's Eve, Ferguson felt he had to act.
Once again, De Gea had been exposed under the high ball, this time allowing Grant Hanley to give Blackburn one of the most surprising results in a season littered with ridiculous scorelines.
De Gea's place was taken by Anders Lindegaard for four games and given he still looked unconvincing on his return, in an FA Cup fourth-round defeat at Liverpool, he might have been condemned to an extended period on the sidelines had the Denmark international not suffered an ankle injury in training that could end his season.
Indeed, when United visited Chelsea a week later, there were some who argued Ferguson would be better served by selecting rookie Ben Amos, who had kept a clean sheet during a midweek win over Stoke.
But Ferguson held his nerve and was rewarded with a magnificent injury-time save from Juan Mata that ensured United's rally from three goals down at Stamford Bridge earned a crucial point.
"He's just stood up as a man," said Ferguson.
"The area where he's been criticised was the aerial ability in the box.
"He should have dealt with the last corner against Blackburn better. He knew that.
"He has addressed that section and it's a great improvement."
That does not mean De Gea is suddenly dominating his penalty area in the way legendary United keepers Peter Schmeichel and Edwin van der Sar used to.
However, he is starting to understand the need to impose his presence in penalty box situations and, at just 21, he has plenty of time to learn.
"It took him time to adapt to the different ways of the English game and he is showing that now," said Ferguson.
"The other night (against Fulham) he made two or three really terrific punches and blocks in the first and second half when they started to propel the ball into the box.
"He has shown fantastic improvement. We expected his ability to show and we are seeing that now."
Indeed, Ferguson believes De Gea is showing the same character traits exhibited by Blackburn manager Steve Kean, who has earned widespread praise for the dignified manner in which he has carried out his duties in the face of severe pressure from his own supporters.
"It's similar to what we were saying about Steve Kean," said Ferguson.
"He got a grip of it and stood up to the challenge.
"He didn't let it get to him and now the boy is playing with confidence. And confidence is a great factor in football."
Following Manchester City's failure to beat Sunderland, United now have a chance to tighten their grip on the title race.
Their next three fixtures - against Blackburn, QPR and Wigan - pit them against sides mired in relegation trouble, the one after that an Aston Villa outfit in freefall.
However, the first three of those sides have won two of their last three games.
So nothing will be taken for granted.
"We know how quickly football can turn on you and bite you," said Ferguson.
"You can look at all the fixtures and say all those teams are fighting for their lives. And they are the kind of games you know will be tight."
Ewood Park has never been an easy place for United.
Ferguson's team have emerged victorious on just two of their last 11 visits, a record that is worse that against any other north-west rival, including Liverpool and Manchester City.
Two seasons ago, United were held to a goalless draw that ultimately cost them any hope of retaining their title.
And even last year, when they only needed a point to get it back, the Red Devils required a late Wayne Rooney penalty to start the celebrations.
"The game at Blackburn has always been difficult," said Ferguson.
"It is a local derby and tends to be a bit feisty.
"Last season we were lucky enough to come back from a goal down to win the league.
"But it will be a very difficult game. That is the way it is going to be from now until the end of the season."