Assistant coach Ricardo Loubscher is confident South Africa have learned hard lessons at the Rugby World Cup after their early defeat to Japan.

The Springboks were on the wrong end of one of the World Cup's biggest shocks in the opening round of fixtures in Pool B as they were beaten 34-32, but they have bounced back to qualify for the quarter-finals.

Victories over Samoa, Scotland and the United States ensured top spot in the pool and a quarter-final against either Australia or Wales on October 17.

Loubscher believes the two-time world champions are well prepared for either opponent, saying their experience against Japan has helped them find their rhythm.

"We just have to make sure we prepare well," he said. "Both teams are in a good space, their confidence is up. 

"We just need to make sure that we regroup; we've learned a lot of hard lessons over the last three weeks in terms of our results.

"I must say we showed a lot of character to come back after the Japan loss. Everyone showed what we're made of, as players, coaches and management.

"The pressure's still on. Next week is going to be different, the stakes are higher in terms of what we need to produce."