Real Madrid are keen on signing Benfica goalkeeper Jan Oblak over the summer as back-up to Iker Casillas, according to reports in Portugal.

The 21-year-old, who joined Benfica from Olimpija Ljubljana in 2010, is among the talented young stoppers who have emerged out of European in recent years. He started last season's campaign on the bench, but earned his place in Jorge Jesus' starting line-up throughout the season – he made his debut in December and has since notched up 16 league appearances.

Casillas' recent performances have once again opened up the Real goalkeeping debate as the Spain goalkeeper - who had played just 1.994 minutes at Real this campaign - conceded five goals in Spain's group B opener against Netherlands.

Real are in the market for successors to Casillas - who has been linked with a January move away from Santiago Bernabeu with Arsenal and Manchester City thought to be interested parties - and the highly-rated stopper Oblak is one of the first names on Los Blancos' wishlist – his youth and potential would make him a great long-term signing, capable of being the replacement when the Spain and Real captain's contract ends in three years.

Los Blancos have been monitoring the Slovenian keeper's situation even though he has another four years left on his deal at Estadio da Luz, with a €20m release clause. And, according to Portuguese daily newspaper A Bola, Real would have already held talks with his agent aimed at securing his services ahead of the next campaign.

The Spanish giants are trying to secure his services to put him on loan for one or two more seasons in Lisbon. However, City rivals Atletico Madrid are also keeping tabs on Oblak - who has made three appearances for his country - as Thibaut Courtois is likely to return to Chelsea next season.

Valencia are also reported to want the keeper and Spanish newspaper Daily AS claims they have already offered €15m for him.