South Africa veteran Schalk Burger says the two-time champions must “write off” their stunning World Cup loss to Japan and urgently find a way to rebound.

The veteran loose forward was in the back-row as the Springboks lost 34-32 to Japan in Brighton on Saturday in the biggest upset in World Cup history.

South Africa now face a big danger of not qualifying from Pool B if they do not win their next match against Samoa in Birmingham on Saturday.

“We need to write it off and move forward as quickly as possible,” Burger said as the South Africans came under heavy fire from back home after the extraordinary defeat.

The criticism included calls from South Africa’s main trade union for coach Heyneke Meyer to be fired. There was also widespread anger among fans over the Springboks’ disastrous start to the World Cup.

Burger said South Africa had to analyse and fix what went wrong so the team can compete against Samoa.

“The first thing to understand is why we lost, why Japan put us under so much pressure,” the 32-year-old Burger told a press conference at South Africa’s team hotel.

“As soon as we understand what the weaknesses are that were exposed in that game, we can move forward. That must happen fast.

“Tomorrow we need to put the game behind us and focus on Samoa.”

Burger said the senior group of players – which includes several World Cup-winners – needed to help turn things around.

“I know our self-confidence is not where it should be, but it is up to us as a senior group and a coaching team to get the guys ready to go out and play,” explained Burger, a member of the South Africa side that beat England in the 2007 World Cup final in Paris.

“We can’t just play within our means against Samoa and think we can win,” the 80-times capped Burger said.

“We have to go out there and take the game from them. It won’t be easy. What is quite difficult for us is not to go back into our shells, but rather take this competition by the scruff of its neck and go out and win this match.”

Burger, who plays club rugby for Japanese side Suntory Sungoliath, praised Japan’s effort as “phenomenal” and a major move forward for Japanese rugby union and the global game.

“I’ve got six team-mates that were on the field and obviously after the match we had a group chat with those who can understand English, and they’re over the moon,” Burger said.

“For the last six months they were targeting us and they got it right. Credit to (coach) Eddie Jones, it was a phenomenal performance.

“We were on the receiving end and we will watch this game on the highlights reel for years to come, but for rugby as a whole and for Japan – hosting the next World Cup – it’s the best thing that could have happened.”

However, Burger warned that tough tests still awaited the Brave Blossoms at this World Cup.

“For Japan the next challenge is Scotland on Wednesday.”

Samoa opened their World Cup campaign with a 25-16 win over the United States in Brighton on Sunday.