The Spaniard endured a torrid time between the posts during the 2019/20 season and made a number of high-profile errors, including in the FA Cup semi-final defeat to Chelsea.
"De Gea has the ability to get back to where he was," Ferdinand told TEAMtalk.
"He's shown over the years that he is a class act. He can now have a break for a few weeks and come back with his focus renewed.
"He has the mentality to come back and reach his levels again. We've seen time and again how good he can be. I think he can still be a big player for United, but he has a point to prove again now. He has had tough times before and has come back.
"He's a great goalkeeper and over the years he has been fantastic for United. He was player of the year four out of six years or whatever it was, but if you are not producing the goods over an extended period of time you have to be told and there has to be someone waiting in the wings to come in."