The former Manchester United keeper has been outstanding for Fiorentina this season, having spent a year out of the game after leaving Old Trafford.
Frey told TMW: "I know him by reputation because he has played at a very high level for many years.
"To tell the truth I was a bit skeptical... Because of the inactivity. Being out for more than a year (and at that age) is very difficult for a goalkeeper. I thought he needed more time to get back into shape and adapt to a new context."
Frey then continued: "He's a bit like me. He's also very instinctive, like me."
And to those who accuse De Gea of rarely coming out of his area, Frey replies: "They said that about me too. But a goalkeeper has to make choices in a hundredth of a second. Often, coming out isn't a good idea."