Real Madrid chiefs fear Vinicius Junior will be missing until mid-February.
The Brazil attacker suffered a hamstring injury in the World Cup qualifying defeat in Colombia last week.
It was expected Vini Jr would only be missing for a fortnight.
But Madrid reporter Arancha Rodriguez is stating feedback from Real Madrid is that their star will now be out until mid-February.
It marks a second hamstring injury this season for Vini Jr, with the attacker suffering a similar setback against Celta Vigo.