Gerard Deulofeu's participation in El Clasico is in doubt after the forward suffered an injury in training on Friday.
The 23-year-old strained ligaments in his left knee as Barcelona prepared for Sunday's visit of Deportivo La Coruna.
Barca confirmed he will be out for up to 10 days, which could rule him out of the showdown with Real Madrid on December 23, as well as this weekend's Liga clash.
Deulofeu has struggled for form this season, but coach Ernesto Valverde said last month that he was "not worried" about the Spain international.
Deulofeu has made nine appearances in La Liga this season, scoring on one occasion.