De Gea will replace Edwin van der Sar, who will retire after the Champions League final with Barcelona on Saturday.
Reports claim United and Atletico have agreed on a deal worth around £18.3million with additional add-ons.
Ferguson told Sky Sports News: “We’ve been working on it for quite a while, we identified him a while back as one we should go for.
“He’s a young goalkeeper, very quick, with good composure and presence. He’s an outstanding replacement for Edwin van der Sar.
“We were looking for someone with the same types of qualities. One great quality Edwin always had was his composure and organisational ability.
“David De Gea is very similar that way.”
