Costa was told by the club yesterday that he faces internal action over his red card against Barcelona, for which he was banned for eight games.
Diego Costa did not train with his Atlético Madrid team-mates today. The striker was at the LaLiga club's training ground but, despite Los Rojiblancos confirming that he is not suffering from any kind of injury issue, he was not involved as Diego Simeone's men went through their paces.
Costa no-show follows news of internal rap over red
And AS has learned that Costa's failure to join in training came after Atlético told him yesterday that he faces internal action over his red card at Barcelona for foul-mouthed dissent against referee Jesús Gil Manzano.
With video evidence demonstrating that the Spain international insulted the match official, the club have opted to open misconduct proceedings against the player, who last Thursday was given an eight-game ban for the sending-off.
The 30-year-old was dismissed for shouting "Me cago en tu puta madre" ("I shit on your bitch mother") at Gil Manzano in Atlético's 2-0 league defeat to Barça a fortnight ago - a result that all but ended the side's hopes of winning the Spanish title.
Striker has flopped since returning to Atlético
Costa, who has scored just four LaLiga goals since re-joining Atleti from Chelsea in a 60m-euro deal in 2017, is being heavily tipped to leave the Wanda Metropolitano this summer, with the Chinese Super League shaping up as a likely destination.