Barcelona midfielder Gavi is unlikely to play again this season after the Catalan club confirmed he tore his anterior cruciate ligament while playing for Spain on Sunday.
Gavi, 19, has also suffered an associated injury to the lateral meniscus and will undergo surgery later this week.
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Barça will provide a timeframe on his recovery after the operation, but Gavi is expected to miss the rest of the campaign and is also a major doubt for Euro 2024 and the Olympic Games with Spain next summer.
"Tests carried out on Monday on the first team player Gavi have shown that he has a complete tear of the anterior cruciate ligament in his right knee and an associated injury to the lateral meniscus," Barça said in a statement.
"The player will have surgery in the coming days after which a new medical update will be released."
Gavi was forced off midway through the first half of Spain's 3-1 win over Georgia after landing awkwardly when controlling the ball moments after a collision with Georgia's Luka Lochoshvili.
Spain coach Luis de la Fuente said the incident with Lochoshvili was unrelated to the injury.
The confirmation of the ACL tear has been met with anger by Barça, with sources telling ESPN the club felt it could have been avoided given Spain had already secured their place at Euro 2024 next summer.
Despite that, Gavi was one of just two players to start La Roja's two games during the current international break, against Cyprus on Thursday and then the win over Georgia in Valladolid on Sunday.
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De la Fuente said that the injury was "unfortunate" but that it was not down to overplaying Gavi.
"He was in perfect condition," De la Fuente insisted after the game. "He hadn't played before the international break because he was suspended, he was fresh and in great shape. There was no problem.
"We are all broken, it is as if we lost the game in the dressing room. There is no explanation other than these things happen in life. This is the toughest day in this sport for me, the most bitter."
Gavi has been a regular for Barça and Spain this season, only missing two games -- both for his club -- through suspension. Only Marc-André ter Stegen and Ilkay Gündogan have played more minutes for Barça.
His importance for Xavi Hernández's Spanish champions has grown due to long-term injuries to Pedri and Frenkie de Jong, with the coach calling him the "heart and soul of the team."
Sources also highlight the role he plays in the dressing room, bridging the gap between the veterans of the team and the youngsters coming through, despite still being a teenager himself.
De la Fuente said Gavi didn't think such a serious injury could happen to him.
"Gavi is broken, destroyed," he said. "He didn't think these things could happen to him. When they have not happened to you before, you can think you're not vulnerable, but we are very fragile."
Barça return to action this Saturday against Rayo Vallecano and, despite losing Gavi, they were boosted by the return of Pedri just before the international break. De Jong is also in line to make his comeback this weekend.
Xavi's side then face Porto, Atlético Madrid and surprise LaLiga leaders Girona at home in three potentially season-defining games.