The midfielder started on loan at the Magpies last season from German outfit Borussia Dortmund, and after making a certain amount of starts in the Premier League a clause in the deal was triggered meaning that he was signed on a five-year deal.
Having made a number of starts in the first half of the season, after the turn of the year Merino lost out to midfield duo Mo Diame and Jonjo Shelvey, making only seven league appearances in 2018.
The Spanish U-21 international has been left understandably disappointed with his lack of game time under Rafa Benitez of late, and so Real Sociedad are looking to pounce to bring the player back to his home country.
It is believed that the Basque club are willing to make the player one of their highest earners, and will offer a five-year contract should the deal be accepted by the Tyneside club.
However, in a recent interview with 'nufc.co.uk', Merino insisted that he was happy at the club.