Striker Didier Drogba has been taken to hospital after he suffered an elbow injury in the first half of Ivory Coast's 2-0 World Cup warm-up win against Japan on Friday.
"If it's serious, it's very worrying, he is our captain, one of the best strikers in the world."
Asked if he was concerned the injury could rule Drogba out of the World Cup which begins next Friday, he added: "Yes, I'm worried, of course I am."
The Elephants' key player went down under a heavy challenge from Japan defender Tulio after 15 minutes which left him spread-eagled on the pitch.
After rising groggily to his feet, the Chelsea forward hobbled off clutching his groin and was replaced by Seydou Doumbia.
His absence disorientated Ivory Coast but Japan were unable to take advantage and they slumped to a fourth successive defeat after losses to Serbia, South Korea and England.
Playing only their second game under Eriksson, the African side added the second with nine minutes to play through defender Kolo Toure.
The Africans face Brazil, Portugal and North Korea in their World Cup group, while Japan will take on Cameroon, Denmark and the Netherlands.
