The former Real Madrid keeper has been left on the bench in recent weeks and took to Instagram with a mournful post after being omitted from the starting lineup for Porto's recent Champions League clash against RB Leipzig.

Now 36, Casillas is understandably keen to see out his career in the first XI. And with Simon Mignolet and Loris Karius still struggling to impress at Liverpool, the Reds could emerge as a tempting option.

Rafa Benitez is also thought to be keen on the 167-cap Spain international, despite Rob Elliot's good form this season for Newcastle.