Barcelona have confirmed Brazilian winger Raphinha suffered a hamstring injury in the 1-0 win over Sevilla on Friday night and is unavailable for selection.
Raphinha, who joined Barca last year from Leeds, started the game in midfield but was withdrawn in the 37th minute after holding his leg on the turf with Fermin Lopez replacing him from the bench.
It was only Raphinha's third league start of the season, having impressed in his previous outing against Mallorca with a goal and an assist.
On the injury, manager Xavi said: "We'll know more about Raphinha's injury tomorrow. I hope to have him available after the international break."
A statement from Barcelona released on Saturday reads: "Tests carried out on the first team player Raphinha show that he has a hamstring injury in his right thigh. He is unavailable for selection and his recovery will dictate his return."
The reigning La Liga champions struggled for the breakthrough before Sergio Ramos' own goal in the 76th minute handed them all three points. Barca briefly went top of the Spanish top flight before Real Madrid reclaimed that position by beating Girona on Saturday night.
Barcelona have a short trip to Porto in the Champions League to contend with in midweek before visiting Granada before the October international break snaps into action.
While Barca have not put a timeframe on Raphinha's return, reports in Spain have suggested the Brazil international will be sidelined for around a month. That period of absence would see him miss the Porto and Granada games and most likely matches against Athletic Club and Shakhtar Donetsk after the international break.
Raphinha may target the Clasico in late October as a potential return date. The similarly sidelined Frenkie de Jong is also eyeing up the clash with Real Madrid as the date to return from his own ankle problem.
Spain international Pedri is also injured but Barca are hopeful he will be fit again once club football resumes later this month.
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This article was originally published on 90min as Raphinha at risk of missing El Clasico with hamstring injury.