Now nearing the end of his second season at Old Trafford following an £18million switch from Atletico Madrid, some observers believe it will be his last.
The summer arrival of Jack Butland at Stoke suggests Asmir Begovic will be on the move, with United long since being viewed as a likely destination.
But De Gea has defended his record and believes he has improved since he joined the club, a view shared by boss Ferguson.
The Spanish keeper said: "Of course when you arrive at a new club it is normal there will be low points. The important thing is to learn from them and improve.
"I know I am much better than when I first arrived at Manchester United."
Ferguson added: "David has shown his character because he has taken a lot of criticism, sometimes unfairly.
"What we are good at is developing people. He came to us as a very young man, not used to the English game and unable to speak the language. Also he was still to mature physically.
"But it's like a young kid taking his first steps forward, he wobbles, then gets up, wobbles, then gets up again and eventually he walks.
"The boy is walking now."
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