Real Madrid are assessing the possibility of signing Antonio Rudiger on a free transfer, sources have told ESPN, after being impressed with the defender's performances in their Champions League quarterfinal with Chelsea.

The centre-back -- whose Stamford Bridge contract expires on June 30 -- was first named as a potential Madrid target earlier this season.

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At that point, sources ruled out a move telling ESPN that the links emerged after Rudiger's representatives offered him to Madrid, rather than a genuine interest from the LaLiga club.

The situation has now changed and multiple sources have told ESPN that Rudiger's name is back on the agenda as a possible defensive reinforcement this summer.

Rudiger, 29, is looking for what could be his last big contract after establishing himself as a key member of a Chelsea team that won the Champions League last season.

Madrid had been unwilling to get dragged into an expensive battle for the player, but sources said club executives were wowed by Rudiger's displays against Madrid -- especially in Chelsea's 3-2 win at the Santiago Bernabeu last week -- and are now considering making a move.

With just over two months left on his Chelsea contract there has been no movement on a renewal, and neither has Rudiger committed his future to any of the other top clubs he has been linked with.

ESPN reported last month that Barcelona had met with the player's advisor to discuss a possible move to Camp Nou, but that now looks unlikely with Barca close to agreeing a renewal for Ronald Araujo.

Madrid's first choice centre-back pair this season has been David Alaba and Eder Militao with Nacho Fernandez and Jesus Vallejo as back-ups, although coach Carlo Ancelotti was forced to deploy Dani Carvajal as a makeshift centre-back in the defeat against Chelsea with Militao suspended and Nacho injured.

Madrid had been considering signing a replacement for the out-of-contract Marcelo this summer, but the arrival of Rudiger could allow them to switch the versatile Alaba to left-back instead.