The Blues declined to comment on reports that the 28-year-old had had a disagreement with head coach Antonio Conte and his coaching staff.

Conte on Friday afternoon said he had some undisclosed doubts for the game, but mentioned no names or reasons for potential absences.

Eden Hazard could play in a central striker role in Costa's absence, just as he did against Bournemouth, when the former Atletico Madrid striker was suspended.

Costa helped Chelsea to the Premier League title in his first season in England in 2014-15, but was poor as the Blues title defence ended in a 10th-placed finish last term.

He was also among the players blamed by a section of Chelsea supporters when Jose Mourinho was sacked by the Blues for a second time in December 2015.

Costa was repeatedly troubled by hamstring problems and disciplinary issues in his first two seasons at Stamford Bridge and was repeatedly linked with a return to Atletico.

Costa was earlier this month subject of speculation over a mega money move to the Chinese Super League.

It was rumoured Tianjin Quanjian were prepared to bid £80million and Costa's future could be the main talking point of the winter transfer window, which closes on January 31.

Costa signed a five-year deal on his arrival in July 2014 for £32m, so has two-and-a-half years to run.

He appeared to have overcome his fitness and disciplinary issues under Conte, with whom his relationship appeared strong.

The 28-year-old has scored 14 goals in 19 Premier League appearances this term and was many pundits' player of the championship at the halfway mark.

His understanding with Hazard and Cesc Fabregas, in particular, had troubled opponents to the extent Chelsea won 13 straight games until the loss at Tottenham on January 4.

The trip to Leicester is Chelsea's first Premier League game since the defeat, coming after a FA Cup third-round win over Peterborough, when Costa was among the substitutes.

Now there are doubts over his Chelsea future.

Former Liverpool and Newcastle manager Graeme Souness has said Chelsea "cannot afford" to lose Costa - and warned that Premier League clubs must not ignore the financial clout of Chinese clubs.

The Scot said: "If your head has been turned... you'll be seeing it like 'I'm doing the right thing for my family'. Players have a short shelf life and he could be injured tomorrow. He'll be seeing it like that.

"He's the man who does the hardest thing in football, gets them goals. He puts the ball away regularly, he's a warrior and brings other people into play. He is the biggest loss Chelsea can have if they end up losing him - they cannot afford to lose him."

Souness added on Sky Sports News: "From the club's side it's the very last thing Chelsea need. He's the leading scorer in the Premier League now - lose him and they aren't going to win the Premier League. That's how important he is.

"You like to think sense will prevail and he'll play until the end of the season and sign a pre-contract, if the Chinese are serious. There must be a way around this for both parties to be happy.

"(Chelsea owner) Roman Abramovich is not skint and he won't take kindly to someone coming in with that kind of money and trying to bully him. He'll be greatly upset by the actions of Costa. I would imagine Roman would be up for a fight and would say 'You're staying here'."

Several Blues players have left Stamford Bridge and ended up in the Asian country, with Nicolas Anelka, Didier Drogba, Demba Ba, Ramires and Oscar all heading east - as well as former Blues boss Andre Villas Boas.

On the spending power of Chinese clubs, Souness, 63, added: "They're blowing us out of the water. These are numbers that the riches of the Premier League cannot match.

"That's where I think we're going. Manchester United and Liverpool, as rich as they are, they're vulnerable.

"Teams in China come knocking with those type of numbers... this may not be the last time we see this situation."