The 20-year-old, who joined Barca last summer from Copenhagen, was injured in training on Monday and could be sidelined for at least six to seven months, according to the Catalan press.
He played just 28 matches last season as he served as back-up to Lamine Yamal and was tipped to leave the club following the arrivals of England winger Anthony Gordon and German international Karim Adeyemi.