Japan captain and Nuremberg midfielder Makoto Hasebe said he was bracing for the worst as he arrived back in Japan on Friday to undergo knee surgery.

The 29-year-old former Urawa Reds and Wolfsburg man has been ruled out of action for four to six weeks following an injury sustained Tuesday during a friendly against Steaua Bucharest at a training camp in Spain ahead of the Bundesliga restart.

"I've never been in this position before so I don't know (when I will be back)," Hasebe told reporters after arriving at Narita airport.

"I realize that the risk of getting injured is always right beside you and I am anticipating the worst. I want (the injury) to heal properly and don't want to rush things."

Hasebe, who underwent a scan on Wednesday which revealed a tear in his lateral meniscus, said he was more concerned at keeping bottom club Nuremberg in the German first division than the World Cup, which is still five months away.