Barcelona have taken a serious interest in Antonio Rudiger.

The German defender will become a free agent at the end of this season.

Talks over an extension with Chelsea continue to stall and foreign clubs are now able to sign a pre-contract agreement with Rudiger this month.

Real Madrid, PSG, Bayern Munich and Juventus have all held talks with Rudiger's representatives.

Sky Sportssays Barca are now making a serious play to sign Rudiger as a free agent next summer.

The club's struggling finances means they are currently unable to compete in expensive transfer bidding wars.

However, a free agent deal would be feasible for Barca chief Joan Laporta.

Now 29, Rudiger is hoping to sign one last big contract before entering the twilight years of his career.

So far Chelsea have resisted his demands to become the Premier League's most expensive defender.

That is despite Rudiger playing 20 times this season under Thomas Tuchel, the most of any Chelsea outfield player.