The Spaniard endured a difficult start to his career at Old Trafford in 2011 as he struggled to adapt to the physical demands of the Premier League.
However, in the last 18 months, the 22-year-old has earned a large number of plaudits for the improvements that he has made to his game.
The latest to praise him is Mexican striker Hernandez, who has compared De Gea to former United keeper Edwin van der Sar.
"He's a wonderful goalkeeper, for me he's probably the best one in the world. People don't like to say that but, for me, he probably is. David and Edwin van der Sar are two of the best goalkeepers I have trained with - wonderful. Same level, same style and David is improving day by day," he told the club's official website.
De Gea started his career with Atletico Madrid, where he was part of the 2010 side that won the UEFA Cup.