Chelsea's Diego Costa is not learning Chinese - Cesar Azpilicueta

Chelsea forward Diego Costa is not learning Chinese in his spare time, teammate Cesar Azpilicueta said as he addressed "rumours" that his fellow Spain international could move to the Chinese Super League.

Costa -- who recently denied reports in Spain that he had reached a pre-contract agreement to join Tianjin Quanjian in the summer -- is under contract at Chelsea until 2019.

"It's all rumours that come out," Azpilicueta told Cadena Ser radio. "No, he is not learning Chinese. He is learning Spanish!"

Striker Costa, born in Brazil, competed for his adopted country at the 2014 World Cup and at Euro 2016.

And Azpilicueta said: "He wants to win the Premier League with us and I don't see him, like you say, learning Chinese.

"I really hope he stays for a long time. He is giving so much to the team, not just goals. He helps create play. He is a reference player for us."

Azpilicueta added, however, that playing in the Chinese Super League was a temptation for many footballers.

"It's a new market and there are many players that have decided to embark on that adventure," he said.

"Each player has his own personal circumstances and different situations in his respective club and he makes that decision."

Brazilian midfielder Oscar left Chelsea for Shanghai SIPG earlier this year in a £60 million deal.