Chelsea striker Diego Costa is facing a fine of up to £300,000 having failed to report to training over the last two weeks, the Sun have reported.
The Spanish forward was due to join up with his teammates a fortnight ago, but has been seen partying in Brazil.
Costa, who had been told by manager Antonio Conte that he would be training separately, was set to return to work on his fitness and to keep himself in shape.
The 28-year-old could now receive a fine of two weeks wages, with his current earnings said to be £150,000 per week.
Chelsea are reportedly concerned that Costa's deteriorating fitness levels could put off potential suitors, after he was informed by Conte that he is no longer in the club's plans.
Costa's situation has been complicated by his desire to return to Atletico Madrid, who are currently under a FIFA-imposed transfer embargo until January.
He has now opened legal proceedings against the Blues after complaining that a move to Atletico has not been sanctioned.
Costa has also accused Conte and Chelsea of informing him that he would leave the club via text during this summer.
But Conte has insisted that an agreement with the striker was put in place in January, when Costa was rumoured to have been set for a switch to the Chinese Super League.
He said: "In January the situation was very clear for the club, the player, for Costa, for his agent that when we arrived in June then it would be finished."
Costa was absent, as expected, for Chelsea's shock opening day defeat against Burnley at Stamford Bridge on Saturday.