Ferguson is confident De Gea will make even more of an impact next season.
"David has developed and matured as the season has gone on," said Ferguson.
"We've seen a very progressive and developing young goalkeeper and next season he'll be even better."
"You have to get used to it. You need a thick skin to be a Manchester United player. Because if you cannot take a battering at times you will fall by the wayside and someone else will fill your shoes.
"He has a huge price tag on his head that carries a lot of weight.
"But he is resilient, even if he still has a lot to prove because this season is not over yet."