TOKYO (AP) — Two weeks ago, Springboks coach Rassie Erasmus described it as a "scary" prospect. It got a whole lot scarier this week.

South Africa is now in Japan's way at the Rugby World Cup and the two-time champion will have to be at its strongest and at its sharpest to avoid becoming another one swept aside by an exhilarated home team and host nation in the quarterfinals this weekend.

Rankings mean nothing. Ask Ireland, rugby's top-ranked team coming into the World Cup and then run off its feet by Japan in a shocking upset in Shizuoka.

Previous records mean zero, too. Ask Scotland, which had beaten Japan in seven out of seven previous tests and led the Japanese early in the last game of the pool-stage before having the carpet yanked out from under their feet in Yokohama on Sunday.

Japan is in the quarterfinals for the first time and the scene may never be better set for such an outsider to threaten the Rugby World Cup final. Beat South Africa, as Japan has done before at the World Cup, and then it's Wales or France for a place in the final. Seems outlandish, but tell Japan that after all that's happened.

If the Springboks and Erasmus didn't see it coming, it's not because they haven't been warned.

They were asked countless times through their pool-stage games what they thought of the possibility of playing Japan in the quarters. For the most part, they answered in typically cautious fashion: It's not decided. It could still be Ireland or Scotland. We haven't thought that far ahead.

The one moment Erasmus did let his guard down was on the day Japan upset Ireland. The Springboks were playing Namibia in Toyota City and Erasmus was late for his team's on-field warmup. He was watching Japan vs. Ireland on TV somewhere in the stadium and he couldn't take his eyes off it.

It was then that Erasmus conceded playing Japan was "a realistic option. And also a scary option."

The Springboks have two memories of Japan in test rugby and they couldn't be further apart. There's the so-called Miracle of Brighton, when the Japanese left rugby flabbergasted by beating the Springboks at the 2015 World Cup.

But what of the most recent meeting? Three weeks before Japan stunned the World Cup again to beat Ireland, it played South Africa in a World Cup warmup game in Kumagaya. The Springboks won 41-7 and the Japanese seemed meek. They were nothing like the ferocious, non-stop force they were against Ireland and Scotland.

Erasmus said the idea behind the warmup game was to "erase the Brighton game" in case the were another meeting in the playoffs, and "that game hopefully doesn't get mentioned again."

Of course, he knows that's not going to happen. The upset of '15 will be mentioned frequently for at least another week.

Also, there's the chance the Japan squad intentionally played within themselves in Kumagaya, so as not to give everyone an early warning of their threat. Or could have been leg-sore from heavy conditioning in training, all designed for fitness to peak in the World Cup.

"Only time will tell. I must say that in that warmup game, there was no pressure," Erasmus said. "It was a warmup game, and the way Japan have embraced the pressure, it's really impressive. The way they have built and accepted the pressure . that will be something massive on Sunday, which will play a big role.

"It will be interesting to see how both teams handle the pressure and expectations on both sides."

Veteran Springboks prop Tendai Mtawarira is looking at this Sunday's game at Tokyo Stadium only in isolation.

Asked if South Africa would like some revenge for the Brighton upset, Mtawarira consigned that game to the past.

"This is an entirely new challenge. I am looking forward to it. It's a big one," he said. "The Japanese team have really been performing well and it's going to be a big one.

"They are unbeaten so far, and they have been great hosts. So, for us, it's a massive, massive game."

Mtawariri said it was important for the Springboks to stick to their strengths, and not be goaded into taking on Japan at a frenetic pace.

"We know the style of rugby we like to play, so the challenge is to not get sucked into their game. We must play our game," he said.

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AP Sports Writer John Pye in Tokyo contributed to this report.

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