Atletico Madrid says Diego Costa sprained his left ankle in the team's 2-1 loss in a friendly against Beitar Jerusalem on Tuesday.
Costa left the field on a stretcher in the first-half of the match in Jerusalem, which marked his return to the squad after missing the final part of the season because of a suspension.
Atletico says initial tests showed no bone damage in the striker's ankle. More exams will be conducted after the team returns to Madrid to assess any possible ligament damage.
The setback was the latest for Costa in a season marred by injuries and lacklustre performances.
Atletico's goal in the friendly was scored by Antoine Griezmann in his last match with the Spanish club. The France forward has decided to leave Atletico but is yet to announce his new club for next season.