David Moyes arrives at United this summer to kickoff a new era with the club.
De Gea said: "I am very proud to have had the privilege of working with Ferguson, it was a real pleasure.
"He is the best coach of all time and it is something I will be able to tell my children and my grandchildren.
"The best advice that he gave me was to simply give my all.
"He told me to continue with the same mentality I have always had. I owe a lot of my capabilities as a goalkeeper to him."