Barcelona forward Martin Braithwaite will need surgery on his left knee, the Catalan club said Monday.
Barcelona said the Danish player has not responded well to conservative treatment and will undergo surgery in the coming days.
Barcelona did not say how long Braithwaite is expected to be sidelined.
He had made three appearances in the Spanish league this season, scoring twice and setting up a goal in Barcelona's opening 4-2 victory over Real Sociedad.
Barcelona hosts Bayern Munich in its first Champions League match of the season on Tuesday. The team's next Spanish league match is next Monday against Granada.