Casillas will become a free agent when his deal with Porto expires at the end of this season, and Sport reported Liverpool are interested in recruiting him as competition for Loris Karius (h/t the Mirror's Liam Prenderville).
Karius has cemented his place as manager Jurgen Klopp's first choice between the posts, and Prenderville wrote that former No. 1 Simon Mignolet is "set to depart" when the transfer window re-opens in June.
It would be almost fitting that Liverpool should recruit Casillas after ousting his Porto team from the UEFA Champions League round of 16 this season, which could yet be his last in the competition, via BT Sport:
According to Corriere dello Sport (h/t Prenderville), Real's interest in AS Roma goalkeeper Alisson Becker, as well as the Italian club's valuation of the player, has led Liverpool to shift their transfer market focus.
And it now appears Klopp could move for a highly regarded deputy to apply pressure on Karius rather than move for a more expensive starting option like Alisson, who is said to boast a price tag of £80 million.
Casillas is as experienced as they come, having accumulated 724 appearances for Real before he left for Porto in the summer of 2015. He initially signed a two-year deal in Portugal before taking up the option of a third.
The deal could be complicated for Liverpool, however, considering Porto have shown an inclination to extend their stopper's stay even further, per Metro's Portuguese football expert, Jan Hagen:
Jan Hagen @PortuBall
Porto president Pinto da Costa on Iker Casillas, who is finally back as first choice goalie after a few months warming the bench, and his expiring contract: "I want to[renew], yes. Who wouldn't? We are happy to have him and Iker is showing that he would be an asset to any club." https://t.co/u4LJRE574t
Another major issue is that the Spaniard is set to turn 37 in May, and while one could argue the value his wisdom and nous could bring to Anfield, there will come a point at which he'll begin to decline.
Klopp appears content placing his faith in the improving Karius for the time being at least, and Casillas held a good account of his abilities against a second-string Reds lineup last month:
Many on Merseyside would prefer to see their club make a significant investment in a new face between the posts, with Karius showcasing his own share of shaky moments since arriving from Mainz in 2016.
Spanish icon Casillas is also bound to have a selection of lucrative options at the end of this season, but Liverpool could snag a good deal for a wizened great if he wishes to sustain a career at the elite level.