Japan's preparations for the World Cup have been dealt another blow after midfielder Makoto Hasebe aggravated an injury in training.
The 26-year-old Wolfsburg man picked up a problem in his lower back during last week's friendly game with the Ivory Coast, which Japan lost 2-0.
Hasebe made nine starts during World Cup qualifying but he was taken to hospital after aggravating the knock, and could miss his side's opening tie against Cameroon next Monday.
A Japan national team spokesman said: "He hit his back against the Ivory Coast and he has gone to hospital as the pain is bothering him."
The news is another blow to Japan's preparations for the South Africa tournament, as the Blue Samurai have lost their last four matches.
Meanwhile, defender Yasuyuki Konno is recovering well from a knee injury suffered against the Ivorians and could be fit for Japan's first Group E clash.
Takeshi Okada's men also take on Holland and Denmark in the group stage, and are trying to arrange a final friendly game against Zimbabwe on Thursday.