The Spaniard, who joined in a £17m deal from Atlético Madrid in 2011, has established himself as United’s first-choice goalkeeper amid competition from Anders Lindegaard.
The 22-year-old was particularly impressive in the second half of the campaign as the Red Devils won the top-flight crown, and Hernández has been impressed by the shot stopper.
“David had to be up there with the best players in the world right now,” Hernández told United’s website.
“For me he’s the best goalkeeper in the world because we all talk about development and having to go down a certain career path and, of course, at his age many people would have been scared to give him the place he’s earned for himself.
“But I think that this season he’s really benefitted from being given the opportunity to play on a regular basis.
“He was first choice between the sticks and I think that any player in the world shows his true ability when he gets the chance to have a decent run of games in the side, and David has really shown his quality.”
And United winger Antonio Valencia backed De Gea to break into Spain’s senior side after the Red Devils goalkeeper recently won the European Under-21 championship in Israel.
“He’s been perfect in everything he’s done,” said Valencia.
“It’s incredible what he’s achieved. He’s shown once again just what an important keeper he is for Manchester United. He’s not far off breaking into the full Spanish national side.
“He is proving here at United that he is one of the best goalkeepers around and I think that all of his team-mates are really happy and pleased to have David in such top form and we hope to be able to enjoy that for a long time to come.”