Werder Bremen president Jurgen Born has warned rival clubs that star playmaker Diego is not for sale at any price.

The 23-year-old Brazil international has been one of the most impressive performers in the Bundesliga this season and has been linked with a move to Chelsea and Real Madrid.

But the former Porto midfielder, who signed a one-year extension to his deal at the Weserstadion earlier this season, is under contract until 2011.

Werder are already resigned to losing Tim Borowski to Bayern Munich in the summer and Born is determined the club's most prized asset will not also leave.

He said: "If someone wants to buy Diego, they have to kill me first. Diego will only leave Werder over my dead body. No one has rang me from Madrid - neither regarding Diego nor any other Werder players.

"Diego is not for sale. He has a contract with us until 2011 and is the most important player in our team."

The player admits he has spoken to fellow Brazil international Robinho about Real Madrid, but has not had any contact with the club.

He said: "My friend Robinho has told me that Real Madrid are a huge club and I know Real coach Bernd Schuster speaks very highly of me.

"When someone wants to open negotiations over me we will see what happens. But I have no agreements with any other club - neither with Real nor with [Serie A side] Juventus."