Barcelona midfielder Frenkie de Jong is set to be out for over a month with an ankle injury and is a major doubt for October's Clásico against Real Madrid, sources have told ESPN.

De Jong, 26, sustained the injury in the first half of Saturday's LaLiga match against Celta Vigo, with Gavi taking his place as Barça came from behind to win 3-2.

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Barça host Madrid on Oct. 28 at the Olympic Stadium, with sources saying it is unlikely De Jong will be back in time for the game.

Before then, Barcelona have four more league games, starting with Mallorca and Sevilla this week, and two Champions League group stage fixtures.

De Jong will also miss Netherlands' upcoming Euro 2024 qualifiers against France and Greece in October. "It's a big loss," Xavi said in a news conference on Monday.

"It's a tough one because of the way we play and the level he has been at. He's a key player for us, he has been really good since last season.

"We have options to come in for him, so hopefully we won't suffer too much. We will see how he is after the [October] international break. That's all we can say for now."

De Jong joins Pedri on the sidelines for Barcelona. The Spain midfielder has been out for a month and there is currently no timeframe for his return, although he is closing in on a comeback.

"Pedri is feeling good, so we will see when we can get him back," Xavi added. "We have options without [Pedri and De Jong], one of them is Sergi Roberto and another is Fermín López."

Barça's win over Celta moved them to the top of LaLiga at the weekend after Real Madrid lost to Atletico Madrid on Sunday.

Xavi's side travel to Mallorca on Tuesday and then host Sevilla on Friday, while Madrid play Las Palmas on Wednesday and Girona, who are now second in the table, on Saturday.