Spain coach Vicente del Bosque says midfielder Xabi Alonso is "a serious doubt" for the World Cup Round of 16 match against Portugal.
Alonso suffered a right ankle sprain during the European champion's 2-1 win over Chile on Friday and his condition hadn't improved much by Saturday night.
Del Bosque says "he's a serious doubt to play on Tuesday. He's already undergoing treatment and we can only hope he'll be ready. If not, someone else will play."
Spain is also without defender Raul Albiol, who injured his right leg during Saturday's training.
Striker Fernando Torres is also nursing a right leg problem but is expected to recover in time for the match at Cape Town's Green Point Stadium.