The 37-year-old goalkeeper rose through the Real Madrid youth system and spent a successful 16 years with the club, winning five LaLiga and four Champions League titles, before leaving for Porto in 2015.
Casillas contract with the Portuguese giants is set to expire at the end of the season, he expects to extend the deal for another two years.
However, he dreams of returning to his homeland to add to the 510 appearances he has already made in the top-flight.
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“I have been lucky enough to compete in La Liga and unfortunately I am not there at the moment.
“What I did with Madrid will be difficult to relive, and to repeat those successes would be very complicated.
“My time at Madrid is in the past, but I would love to return to La Liga,” he told reporters on Monday.