The 20-year-old goalkeeper, who moved to Old Trafford from Atletico Madrid over the summer, came under fire for his performance at the start of the season but has begun to find form.
"He is an unbelievable player like the rest of the team, but he is improving each day and wants to work," Chicharito told MUTV.
"He knows to be playing in the shirt of Manchester United is a big responsibility, but he is enjoying it and is doing very well.
"David is a very good goalkeeper and is improving day-by-day. He is still very young, 20 years old, and can play for 20 more years if he wants."
De Gea and Hernandez are currently en route to Romania to face FC Galati in the Champions League tomorrow night.