De Jong missed Friday’s 0-0 draw away to Sevilla with coach Quique Setien saying before the game he was leaving the player out as a precaution.
Barcelona midfielder Frenkie de Jong is set to miss the team's next match against Athletic Bilbao after the club said in a statement on Sunday he had injured the calf muscle in his right leg.
Dutch international De Jong missed Friday's 0-0 draw away to Sevilla which dented Barca's hopes of winning the Spanish title, with coach Quique Setien saying before the game he was leaving the player out as a precaution.
The injury proved worse than feared as the club released a medical report on Sunday, saying the player was unable to train although did not say when he would be able to return.
Barca lead Real by three points in the standings but have played one game more than Zinedine Zidane's side, who will go top of the table if they beat Real Sociedad later on Sunday.
Setien's side visit struggling Celta Vigo after Tuesday's match against Athletic before a crunch home game against third-placed Atletico Madrid the following Wednesday.
De Jong joined Barca from Ajax Amsterdam last year for 75 million euros ($83.81 million) and has appeared in 27 of their 30 league games this season.