United legend Van der Sar believes fighting back from being dropped last season will prove to be a turning point in his career.
The Dutchman said: "I think that is the way everybody has seen it.
"The first half of the season and the year before, there were some mixed feelings. The gaffer changed it up a little bit to play Anders Lindegaard for three or four games.
"But then David came back in and we stuck with him.
"From that point, his performances grew and he became more important to the team all of the time.
"It has been a good turn around for him in terms of his performances and his own self-confidence in being the Manchester United goalkeeper."
De Gea was named in the PFA Team of the Year for his performances as United won the title.
And Van der Sar added: "Of course, the PFA recognition was great but the main thing you want is to win the Premier League.
"Personal accolades are nice but the main thing is winning something with the team. That was always my preferred choice.
"As long as your team-mates are happy with you and your manager plays you every week, those are the best accolades you can get.
"Of course, after you win the league it is nice to look at individual trophies but the team always comes first."