Barcelona forward Ansu Fati arrived at the Quirón Clinic in the city shortly after 10am on Monday ahead of the operation he will undergo on his knee injury.
Ansu, 18, tore the meniscus in his left knee in Saturday's 5-2 win over Real Betis and will be treated by Doctor Ramon Cugat with the supervision of the club's medical staff.
It won't be until after the operation that Barça will know exactly how long they will be without the Spain international, who has enjoyed a great start to the season.
However, it will be months and not weeks until Ansu is back, with the teenage star not likely to feature again until at least 2021.
The most optimistic predictions suggest he will be out for two months, while the most pessimistic ones lean towards three to five months on the sidelines.
Barça will reveal more later on Monday.