Japan officials confirmed the injury to the 30-year-old Tanaka, who did not face Germany in Tuesday's friendly, with the Jubilo Iwata player returning to his homeland for treatment.

Japan coach Zico is expected to call up FC Tokyo defender Teruyuki Moniwa, 24, as a replacement for Tanaka.

Zico also has concerns over striker Akira Kaji who was stretchered off in the 39th minute of Japan's 2-2 friendly draw with Germany in Leverkusen on Tuesday.

Kaji, capped 43 times, was clutching his knee after a tackle from behind.

Japan, who reached the last 16 of the 2002 World Cup, open their campaign with a game against Australia in Kaiserslautern on June 12.