Real Madrid captain Iker Casillas has emerged as a shock target for Manchester United. The Telegraph says United are actively searching for an experienced and imposing goalkeeper to replace David de Gea at the end of the season.

While the club have recently scouted Stoke's Asmir Begovic and Galatasaray's Uruguay international, Fernando Muslera, it is understood that there is no outstanding candidate to replace De Gea.

The decision by Barcelona's Victor Valdes to reject a new contract at Barcelona will ensure that United consider the 31-year-old, while the uncertain future of Real Madrid's Casillas could present United manager Sir Alex Ferguson with the opportunity to recruit a goalkeeper regarded by many as the best in the world.

Both Barcelona and Real are monitoring De Gea's situation because of persistent rumours of his unhappiness in Manchester.