Spain international striker Diego Costa refused to take part in training on Thursday after learning that Atlético Madrid had opened internal disciplinary hearings following his red card against Barcelona.
The 30-year-old was handed an eight-match ban the footballing authorities after he launched a foul-mouthed rant at referee Jesús Gil Manzano.
The club have also decided to explore options to punish Costa even further, and AS claim that the striker refused to train with his teammates after learning of Atlético Madrid's intentions to take matters further.
Atlético have already confirmed that Costa isn't struggling with an injury.