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Costa joined the Blues from Spanish club from Atletico Madrid for £32m in 2014

Striker Diego Costa has been left out of the Chelsea squad to face Leicester on Saturday after a dispute with a coach over his fitness.

The Spain international has not trained for three days and has not travelled for the Premier League leaders' match with the champions (17:30 GMT).

The news comes amid reports he is the subject of an offer to move to China that would be worth £30m a year. external-link

Costa, 28, has scored 14 goals and provided five assists this season.

Chelsea declined to comment.

It is understood Blues owner Roman Abramovich is not interested in releasing him from his contract, which expires in 2019, and would not entertain the idea of being forced to do so.

Speaking in early January, Costa admitted he wanted to leave Chelsea last summer, but said he was now happy to stay.

Chelsea had been hopeful of agreeing a contract extension with the Brazil-born forward, but the dispute with fitness coach Julio Tous raises new doubts.

Diego Costa's record in Premier League matches for Chelsea

Costa joined the Blues for £32m in 2014, and was understood to be close to a return to former club Atletico Madrid after a difficult 2015-16 campaign.

"Did I want to go? Yes, yes, I was about to leave," he said earlier this month. "But not because of Chelsea.

"There was one thing I wanted to change for family reasons but it wasn't to be, and I continue to be happy here."

Shortly afterwards, manager Antonio Conte said he believed the striker was now "completely focused" on "fighting for this club and for his shirt".

He added: "When Diego decided to stay, I wasn't concerned. He is showing great patience in the right way, in every moment of the game."

Midfielders Jon Mikel Obi and Oscar recently left Chelsea for Chinese clubs - Tianjin TEDA and Shanghai SIPG respectively - while ex-Manchester City and United striker Carlos Tevez joined Shanghai Shenhua from Boca Juniors in a deal reportedly worth £310,000 a week.

'Costa has no affinity with England' - analysis

Former England defender Danny Mills on BBC Radio 5 live

Why shouldn't Diego Costa go to China? There is no loyalty from clubs in football.

He's already defected from Brazil, his native country, to play for Spain and has no real affinity with England and the Premier League. I'm sure he likes London but he doesn't have any real affinity here.

Brazilians move around all the time; they will go wherever the money is.

This is how the Premier League started, paying huge money for foreign stars and now China is trying wrestle the Premier League away from England.

In general, how many England players have gone abroad in the past? We like our creature comforts. Brazilians are quite happy to up and leave.

Diego Costa has got no loyalty or affinity with England and the Premier League and you can't blame him - everybody would do the same thing.

Former England midfielder Jermaine Jenas on BBC Radio 5 live

Everything has been smooth sailing for Chelsea up to now. Imagine the faces of Manchester United boss Jose Mourinho, Liverpool manager Jurgen Klopp and Mauricio Pochettino at Tottenham. This is what they have been waiting for.

Another bid from the Chinese market seems to be rocking the boat of another top club. It's a huge problem.

When these situations arise, the players are probably thinking they'll go and do two years and then come back and play in the Premier League. Financially, they're not just supporting their immediate family, they are supporting their whole family… aunts, uncles and cousins.

I'd still give Chelsea a good chance of winning the title even if they lost him. With the lead they now have, I think they can cope if they replace him.

You don't want to keep players at your club who don't want to be there. Yes, Costa has been a huge part of Chelsea's success but he's not Lionel Messi or Cristiano Ronaldo.

Everton winger Yannick Bolasie on BBC Radio 5 live

Diego Costa is a problem for any defender. He is strong, quick and doesn't stop running. He sets the tone for all the other Chelsea players.

It's frightening the way the Chinese market is acting right now.