Casillas, 36, joined Portuguese giants Porto from Real in the summer of 2015 after losing his grip on the number one spot at the Bernabeu. After a couple of forgettable final years in the Spanish capital the World Cup winner has enjoyed something of a revival at the Estádio do Dragão, though he is yet to add to his vast trophy haul with Liga Nos league leaders and was recently relegated to the substitutes' bench by manager Sérgio Conceição.
Casillas' current contract with Porto expires next summer, and a report from Spanish pulbication El Pais, relayed by the Mirror, claims that Liverpool may try and make a move for the illustrious Spaniard in January, with Simon Mignolet and Loris Karius failing to impress during the embryonic stages of the new campaign.
Mignolet showed signs of improvement last season after battling to keep his place between the sticks at Anfield ahead of Karius, who has looked wildly unconvincing since joining Liverpool from Mainz in the summer of 2016, but the Belgium international's howler in his side's 4-1 defeat by Tottenham has led to calls for Danny Ward to be given a sustained run in goal for Klopp's side, who face newly promoted Huddersfield Town on Saturday.
Liverpool's defensive woes do not just lie in goal. Centre-back Dejan Lovren was hooked on half an hour against Tottenham after serving up a wildly poor display in which he was culpable for Spurs doubling their lead. Reds legend Phil Thompson believes it may be time to axe the former Southampton star, who has been struggling with an Achilles problem in recent weeks, but Klopp has little to choice but to stand by the Croatian, who signed a new £100,000-a-week deal just a few months ago.