Ousmane Demeble has been ruled out for up to four months in an injury blow that has rocked Barcelona.
Dembele had to be withdrawn in the first half of his side's dramatic win, leaving the field after sustaining the problem while attempting a back-heel near the corner flag when the match was still goalless.
After conducting tests on Sunday, Barca released a statement which read: "The tests have come back following first team player Ousmane Dembele has ruptured the tendon in his femoral bicep in his left thigh.
"The player will be operated on by Dr. Sakari Orava in Finland this week. He is expected to be out for between three and a half months and four months."
The problem, which is in Dembele's left leg, will see him miss the first half of the season in a huge blow to the Catalans after his initial €105million move from Borussia Dortmund.
Barca, who have won all four of their La Liga matches to start the new season, have clashes against Eibar, Girona, Sporting CP and Las Palmas before the next international break.
Dembele is also set to miss huge league fixtures against Atletico Madrid, Sevilla, Valencia and the rest of the Champions League group stages.
The France international is also in line to miss the first league Clasico of the season against Real Madrid in December, with his return coming after the mid-season break.
Dembele had made his first Barca start against Juventus in the Champions League on Tuesday, having come on as a substitute at home to Espanyol last week, his first game in the club's colours.
WHAT GAMES WILL DEMBELE MISS FOR BARCA?
Dembele's injury means that he will miss much of Barca's season, including a host of crucial matches in the league and Champions League, as well as domestic cup competitions such as the Copa del Rey.
Below is a list of games that the 20-year-old is likely to miss, based on his projected recovery timeline.
|Sep 19||Eibar - La Liga|
|Sep 23||Girona - La Liga|
|Sep 27||Sporting - Champions League|
|Oct 1||Las Palmas - La Liga|
|Oct 14||Atletico Madrid - La Liga|
|Oct 18||Olympiacos - Champions League|
|Oct 22||Malaga - La Liga|
|Oct 25||tbc - Copa del Rey round of 32, first leg|
|Oct 29||Athletic Bilbao - La Liga|
|Oct 31||Olympiacos - Champions League|
|Nov 5||Sevilla - La Liga|
|Nov 19||Leganes - La Liga|
|Nov 22||Juventus - Champions League|
|Nov 26||Valencia - La Liga|
|Nov 27||tbc - Copa del Rey round of 32, second leg|
|Dec 3||Celta Vigo - La Liga|
|Dec 5||Sporting - Champions League|
|Dec 10||Villarreal - La Liga|
|Dec 17||Deportivo - La Liga|
|Dec 23||Real Madrid - La Liga|
|Jan 3||tbc - Copa del Rey round of 16, first leg|
|Jan 7||Levante - La Liga|
|Jan 10||tbc - Copa del Rey round of 16, second leg|
|Jan 14||Real Sociedad - La Liga|
|Jan 17||tbc - Copa del Rey quarter-final, first leg|
|Jan 21||Real Betis - La Liga|
|Jan 17||tbc - Copa del Rey quarter-final, second leg|
|Jan 28||Alaves - La Liga|
|Jan 31||tbc - Copa del Rey semi-final, first leg|