Japan head coach Jamie Joseph has warned his players they must stand tall if they want to survive at the 2019 Rugby World Cup, after wilting under South Africa's aerial bombardment in a defeat on Friday.

The Brave Blossoms went down 41-7 to the Springboks at Kumagaya Rugby Stadium in their final tuneup before kicking off their Rugby World Cup campaign, with South Africa scoring six tries to the home side's one in a comprehensive victory.

Japan struggled to deal with two-time world champion South Africa's attritional power game, with constant kicks from scrumhalf Faf de Klerk and flyhalf Handre Pollard causing havoc in the home team's defense.

Japan now has less than two weeks to address its weak points before it kicks off Asia's first-ever Rugby World Cup against Russia at Tokyo Stadium on Sept. 20, and Joseph warned that pool rivals Ireland and Scotland will pose a similar threat to his team's bid to reach the quarterfinals.

"It wasn't a surprise," Joseph, whose team will also play Samoa in Pool A, said of South Africa's game plan. "Where they had an advantage was in the aerial game. They won their battle in the air. Their outside backs were very good aerially, very skillful and very big, very dynamic in the air. That was the key battle that they won today.

"Our wingers aren't very big," he said. "I think what's important is that that's the type of game Scotland and Ireland will play against us as well, so that's the area that we need to work on."

The match was billed as Japan's chance to inflict another famous defeat on South Africa, having pulled off the Rugby World Cup's biggest-ever upset at the tournament four years ago in England. Japan beat the Springboks 34-32 in Brighton to stun the watching world, but South Africa head coach Rassie Erasmus was pleased to exorcize some demons in the rematch.

"We were under pressure from the beginning because we had that tag around our neck — we lost to them back in 2015," said Erasmus, whose team has been drawn with defending champion New Zealand, Italy, Namibia and Canada in Pool B. "I'm not trying to say something to please the Japanese people, but the way they respect the players on the field, substitutions being made, kickers going for balls, to the way they even applaud the opposition when they do something well, for me and the players it's a new experience.

"When they ask us about 2015, I don't get upset about that," he said. "They're proud of 2015 and they should be proud of 2015. We desperately wanted to turn that around and that's why we picked our best team tonight. Now we are hoping they will progress through the pool and we can see them again in the playoffs."

Japan was hit with an early setback when flying winger Kenki Fukuoka went off with a knee injury in the fourth minute, and No. 8 Amanaki Lelei Mafi also left the field with a shoulder injury seven minutes into the second half.

Joseph said that initial reports suggested Fukuoka had a strained calf muscle and Mafi would be out for one or two weeks, but Japan flanker Pieter Labuschagne believes the team can cope in their absence.

"Both of them are really good-quality players and both have the X-factor, but also the guys who came on for them knew exactly what was expected of them and really made a difference as well," said Labuschagne, who was playing against the country of his birth. "Now it's just getting both those players back, so that we've got our full squad when they want to select the team. Hopefully it's not too serious, but the guys who came on also made a big difference."

Japan did not even get on the scoreboard until the 60th minute, when an interception and then a cleverly improvised pass from center Timothy Lafaele released winger Kotaro Matsushima to race home for a try.

The score briefly gave Japan a new lease of life, but South Africa quickly nipped the nascent revival in the bud and scored two tries in the final seven minutes to run up the score.

"In the last 10, 15 minutes, the score got away from us," Joseph said. "We were behind and we needed to chance our arm. We're the sort of team that wants to go down fighting. But with the pressure that we received, we conceded tries in the last seven or eight minutes, which was disappointing for the players because they gave so much."