The 27-year-old French international has generally formed an excellent partnership with Sergio Ramos over the course of the last decade in Spain, but he is now approaching the end of his current deal with the Spanish champions.
His form has suffered so far this season but he is still one of the most accomplished defenders in European football, and was almost signed by Manchester United before Zinedine Zidane intervened on behalf of Real to secure his transfer from Lens as a teenager a decade ago.
His contract has 18 months left to run but he is far from agreeing a deal to extend his stay in the capital and that might motivate his club to sell him in the summer so as to avoid losing him for nothing in a year and a half. Paris Saint-Germain and Juventus are two clubs who also have an interest in taking him from Real should he become available.
Spanish 34-year-old Ramos is approaching the end of his own contract, which expires this summer, and the veteran has also been linked with a switch to Old Trafford as manager Ole Gunnar Solskjaer searches for an adequate replacement for Victor Lindelof, though in truth the club would still need someone to step in for Harry Maguire who has been a huge disappointment since he arrived from Leicester City a couple of seasons ago.
Real are believed to have a debt of around $1 billion due to the coronavirus pandemic, which has not been helped by their huge wages, and it caused them to forego any signings at all last summer, instead bringing Martin Odegaard back from Real Sociedad, before sending him back on loan to Arsenal in January.