MADRID, Oct. 23 (Xinhua) -- Frenkie de Jong has set alarm bells ringing just three days away from the first Real Madrid vs FC Barcelona clash of the season after the Dutch midfielder missed Barcelona's Thursday training session with a case of gastroenteritis.

De Jong has the same stomach bug that meant defender Andreas Christensen missed Tuesday's Champions League win at home to Olympiakos, with the Denmark international also missing Thursday's session.

Although it is probable De Jong will recover in time to travel for Sunday's El Clasico in the Santiago Bernabeu Stadium, his possible absence is another headache for coach Hansi Flick, who will serve a one-game touchline ban for the game.

De Jong is a fixture in the heart of the Barcelona midfield along with Spain international Pedri, with either Marc Casado or Fermin Lopez taking the final place in the middle of the park.

If De Jong isn't 100 percent fit, Casado would be the logical replacement in the holding role with Pedri and Lopez given more freedom.

There was better news on the injury front for Raphinha and Ferran Torres, both of whom completed Thursday's session with no problems after missing recent matches due to injury.

Dani Olmo, Gavi and Joan Garcia won't be fit for Sunday's match, while Marc-Andre ter Stegen is a long-term absentee for Barcelona after having a back operation at the end of July. ■