Joao Felix will miss Atletico Madrid's derby against Real Madrid after sustaining an unspecified muscle injury to his right leg.
The Portugal forward suffered the setback during Sunday's draw against Leganes.
He missed Tuesday and Wednesday training because he was unable to train with the squad.
The club made a statement: "Joao Felix suffered a muscle injury to his right leg during Sunday's match against Club Deportivo Leganes"
"Given the ongoing pain after the day of rest, the club's medical services have performed tests to diagnose the injury. He is pending response to treatment."
Atletico Madrid are fifth in the table, 10 points adrift of leaders and city rivals Real Madrid.