The 2003 AFC Young Player of the Year, currently on loan at Spanish Primera Liga side Mallorca from J.League outfit Cerezo Osaka, sustained the injury in January when he made an impressive debut for Mallorca, scoring a goal and setting up another in a 2-2 draw with Deportivo La Coruna.

According to Kyodo News Agency, the 22-year-old has sustained a fractured kneecap although he has played through the pain in recent matches including a second-half substitute’s appearance in the 2-0 defeat to league leaders Barcelona on Saturday.

"I still feel pain when extra pressure is put on my knee and it looks like it hasn't healed naturally yet," said Okubo.

Okubo is expected to be back in time for Mallorca’s next league game against Levante on Sunday.

The Mediterranean island side are second from bottom in the Spanish Primera but are just two points from safety after a recent revival of fortunes.