Japan's 41-7 loss to South Africa on Friday in front of 22,258 at Kumagaya Rugby Stadium was made worse by injuries to two of their strike runners, but head coach Jamie Joseph is hopeful the duo will be back soon.

Flying wing Kenki Fukuoka and powerful No. 8 Amanaki Lelei Mafi were both forced from the field, leaving head coach Joseph with some headaches ahead of his side's Pool A opener against Russia in Tokyo on Sept. 20.

Fukuoka pulled up lame away from the ball in just the fourth minute and was seen on crutches later on, while Mafi looked to be holding his right shoulder as he left the field early in the second half.

"Kenki has a strained calf muscle which is not only disappointing but it also affected the team performance as he is one of our best players," Joseph said. "And Mafi took a knock to the shoulder, but should be OK in a week or two."

Despite plenty of possession -- Japan had 64 percent of the ball -- without their speed merchant and battering ram, the hosts struggled to get past a well-organized Springbok defense, getting forced into turnovers on a number of occasions because of the visitors' dominant tackles.

"It was a dominant defensive effort that led to tries from turnovers," said South Africa coach Rassie Erasmus.

But he said it could have been better.

"It was 80 percent successful. There were times when they almost got away and stages where they could have capitalized."

Japan's failure to capitalize was based mainly on the inability of halfbacks Kaito Shigeno and Yu Tamura to provide enough quick ball for the backs and to kick effectively.

Joseph, however, said credit should go to the South African backs who he said dominated "the aerial battle."

"(Pool A opponents) Ireland and Scotland will play like that against us so it is an area we need to work on."

On the bright side, Japan's bench, and in particular Yoshitaka Tokunaga and Yutaka Nagare, did raise the performance of their side and the speed at which they played, while Luke Thompson proved at 38 years old he is in better shape than ever.

Captain Michael Leitch said time would tell how much Japan's confidence had been dented but he was hopeful they would recover in time for the Russia game.

Time will tell.

Related coverage:

Rugby: Brave Blossoms handed lesson by vengeful Springboks

Rugby: Hot, humid Kumagaya welcomes Japan, S. Africa fans