Japan coach Zico has doubts over two of his strikers with just over a week to go before his side's opening World Cup clash against Australia.

Japan play Malta on Sunday in their final warm-up game in Dusseldorf but both Naohiro Takahara and Atsushi Yanagisawa are struggling to be fit for the clash.

Takahara has a sore knee while Yanagisawa is struggling with a hamstring problem.

"These kinds of muscle injuries are always worrying," admitted a concerned Zico.

"We will see what's what in training but I very much doubt either of them will be able to play against Malta.

"I want them to play in the Australia game (on June 12) so we will do our best to have them ready."