According to reports, Real Madrid are interested in signing Chelsea defender and Barcelona target Cesar Azpilicueta. The Spaniard's contract with the Blues will run out in the summer, allowing him to join another club for free. So far, the Blues' negotiations over a new contract have failed.Barcelona were heavily linked with Azpilicueta for a summer transfer and a January pre-contract. However, according to Defensa Central, Los Blancos have joined the fray in pursuit of the Spaniard as well.Fabrizio Romano@FabrizioRomanoBarcelona are working to sign César Azpilicueta as free agent in June. Talks on - contract proposed until 2024 with potential option, as per @10JoseAlvarez. Chelsea are still waiting for César to communicate his decision #FCB Barça are also interested in Andreas Christensen.12:28 PM · Jan 25, 2022248232037Barcelona are working to sign César Azpilicueta as free agent in June. Talks on - contract proposed until 2024 with potential option, as per @10JoseAlvarez. Chelsea are still waiting for César to communicate his decision 🇪🇸 #FCB Barça are also interested in Andreas Christensen.Azpilicueta joined Chelsea in 2012 from Marseille for around £7 million and has been a mainstay in the team since. He has made over 450 appearances for the club in all competitions, scoring 14 goals and assisting 56. He has played in multiple positions as a centre-back, right-back and even left-back at times.Needless to say, he is a great asset in the defense and Real Madrid are looking to take benefit of that. They lost Sergio Ramos and Raphael Varane to Paris Saint-Germain and Manchester United respectively last summer.They only have Eder Militao, David Alaba and Nacho as options in central defense. Hence, a signing like Azpilicueta could be crucial for Los Blancos. It remains to be seen where the Spaniard decides to eventually go.Real Madrid, Chelsea and Barcelona could battle it out for Niklas Sule in the summerAmong a host of defenders becoming free agents in the summer is Bayern Munich's Niklas Sule. The German has refused to sign a new contract with Bayern, which means he will be available as a free agent in the summer.Real Madrid, Chelsea and Barcelona are all reportedly interested in the German.Simon Phillips@siphillipssportChelsea have been in contact with Niklas Sule's representatives this month and the Blues could firm up their interest in the weeks ahead.- @AdamNewson11:53 AM · Jan 26, 20222989161Chelsea have been in contact with Niklas Sule's representatives this month and the Blues could firm up their interest in the weeks ahead.- @AdamNewson https://t.co/8AQaXTrTxCIn addition to Azpilicueta, the Blues also have Antonio Rudiger and Andreas Christensen running out of contracts in the summer. Both players have been linked with Los Blancos and Blaugrana respectively.Hence, one could argue that the Blues would need Sule more than the other two clubs. With Andreas Christensen and Antonio Rudiger's future at the club uncertain, the London club look thin at the centre-back position. While Thiago Silva recently signed an extension, he will soon be 38 and cannot be relied upon to play 90 minutes every week.Meanwhile, Sule is also reportedly being monitored by Liverpool. It could make for an interesting battle come summer for the big German defender.