Japan head coach Jamie Joseph said before Saturday's win over Tonga that he was "80%" certain of who would make up his Rugby World Cup squad when he names it on Aug. 15.

But he admitted after the gritty 21-16 victory over the 'Ikale Tahi at Hanazono Rugby Stadium that, with just one game remaining before he makes the final cut, there would be some sleepless nights.

"It will be difficult to decide who to leave in and who to leave out at the World Cup. We want to perform at our best and take our best athletes with us," he said.