Real Madrid have reportedly identified Manchester United’s David De Gea as a prime summer transfer target.The La Liga heavyweights are unsure of the future of club captain Iker Casillas, who has lost his place in the team, while they are also not certain if Diego Lopez is a player they can rely on for much longer.googletag.cmd.push(function() { googletag.display(“div-gpt-ad-1389116196215-0”); });According to Mundo Deportivo, Madrid have drawn up a list of top young goalkeepers who they deem up to the task of filling the number one jersey long-term, and United’s De Gea is currently the preferred choice.Los Merengues are confident of prizing the former Atletico goalkeeper away from Old Trafford as the English champions look increasingly unlikely to earn a Champions League place for next season.Another keeper high on their list is Espanyol’s Kiko Casilla who came up through the ranks at Real and has been impressive in the last three seasons.The fact that Casilla would be a cheaper alternative to De Gea is a possible advantage for the 27-year old’s chances of being snapped up.Madrid initially had their sights set on Chelsea goalkeeper Thibaut Courtois, currently on loan at Atletico Madrid, but were scared away by the English club’s 25million price tag.