De Gea, 20, has been Atletico's first-choice custodian for the past two years after progressing through the club's youth team and has starred for the Rojiblancos since making his debut in 2009.
The youngster's meteroric rise will continue after Ferguson revealed De Gea is set to leave his hometown club to join fellow Spanish 'keeper Pepe Reina in the Premier League.
"We've been working on it for quite a while," Ferguson said after Gary Neville's testimonial on Tuesday night. "We identified him quite a while back as one we should go for.
"He's a young goalkeeper, very quick, good composure, presence and an outstanding replacement for Van der Sar.
"We were looking for the same type of qualities as Edwin, because the one great quality Edwin always had was his composure and organisational ability. With David De Gea, he is very similar that way.''
Current United No. 1 Van der Sar announced earlier this year that he plans to hang up his gloves at the end of the season, prompting Ferguson to scour Europe for a suitable replacement for the veteran Dutchman.
It took the Red Devils boss some time to find a successor to legendary United goalkeeper Peter Schmeichel after his departure in 1999, with Van der Sar arguably the only man who has managed to suitably fill the large void left by the Great Dane's exit.
But Ferguson feels that De Gea - half the age of Van der Sar - has what it takes to stand between the Old Trafford posts in the Dutchman's place next season, with a deal of around £16 million thought to have been agreed with Atletico.
The Spain Under-21 international was believed to have been weighing up a move for a while, with United privately expressing their interest to Atletico a few months ago.
The likes of Maarten Stekelenburg, Hugo Lloris and Manuel Neuer had also been linked with United, who brought in Danish goalkeeper Anders Lindegaard as added cover from Aalesund in January.
Responding to the news United were closing in on De Gea, Atletico president Enrique Cerezo told Spanish radio station Cadena Ser: "We don't know anything. Officially neither Manchester (United) or the player at this moment have informed us of anything.
"He (De Gea) knows very well that he can negotiate (with other clubs) but always that they have to pay his buy-out clause.''