Seiichiro Maki is doubtful for Japan's first game against Thailand next Wednesday in the Asian qualifying round for South Africa 2010.
The JEF United Chiba forward hurt his right side during a friendly match against Bosnia and Herzegovina on Wednesday to be replaced in the 33rd minute by Koji Yamase, who scored two goals and set-up another in a 3-0 win.
The same 25 players for Japan's two-game warm-up series, also drawing with Chile 0-0 last Saturday, were called up on Thursday for a training camp. They will be reduced to 18 before the Thailand game.
Maki, who has scored seven goals in 28 games for Japan, was still to join the training camp starting later Friday in Chiba.
"I'm all right. No problem. Of course, I will join the team if I'm called up," said Maki.
Japan coach Takeshi Okada abandoned his plan to call up Celtic midfielder Shunsuke Nakamura for the match at the Saitama stadium as Nakamura has just recovered from a knee injury.
Japan's 25-man squad will be spearheaded by former Eintracht Frankfurt striker Naohiro Takahara, who has left Germany for Asian club champions the Urawa Reds.
Takahara, who missed the 2002 FIFA World Cup™ due to a pulmonary embolism, became the best Japanese scorer in Europe in 2006-7 with 11 goals in 30 games, and has scored 23 goals in 55 games for Japan.