The vastly experienced stopper has experienced a turbulent last two seasons, slipping away from his guaranteed starting berth at the Bernabeu.
He has been instead fielded in cup games, helping Real to La Decima – their tenth European cup – at the end of 2013/14.
With Diego Lopez now Los Blancos’ No. 1 and Costa Rican World Cup hero Keylor Navas a target for the club, Casillas is ready to call time on his lengthy spell in Madrid.
Arsenal are rumoured to be interested, and the much-decorated Spaniard is open to the prospect of a new challenger in north London.
Nice’s David Ospina is considered to be the Gunners’ top target, but with late competition from Valencia for the Colombian an alternative may be needed.
Casillas will command hefty wages, but he could solve Arsene Wenger’s long-running search for a top ‘keeper.