Barcelona striker Robert Lewandowski could miss the first Clasico of the season against Real Madrid on 28 October after spraining his ankle in Wednesday's Champions League win over Porto.
Lewandowski came off in the first half of a 1-0 victory and faces up to a month out, according to reports in Spain.
Barcelona gave no indication how long the Poland international would be sidelined, but said he "will be out of action until the injury heals."
He will be unavailable for Sunday's trip to Granada in La Liga, and faces a race against time to return against Madrid at the end of the month.
He is also expected to be ruled out of Poland's Euro 2024 qualifiers against the Faroe Islands and Moldova.
Lewandowski was hurt in a challenge with Porto defender David Carmo, and joins Pedri, Frenkie de Jong and Raphinha on the treatment table at Barcelona.
The 35-year-old has scored six times in 10 games for Barcelona this season, with five of those goals coming in the league.