Japan defender Yasuyuki Konno will miss his country's opening World Cup game against Cameroon on June 14 because of a knee injury.
The 27-year-old suffered the injury to his right knee in Friday's 2-0 defeat by Ivory Coast in a final tune-up for the tournament in South Africa.
"It's ligament damage so he's a doubt for the first game," Japan coach Takeshi Okada told reporters before his squad left their Swiss training camp.
"He's probably looking at two weeks (out). He is walking normally now but it''s best not to risk him for the first game."
Japan are coming into the tournament on the back of a four-match losing streak and face the Netherlands and Denmark following their Group E opener against Cameroon.
