South Africa all but sealed a spot in the World Cup quarterfinals with a 49-18 victory over Tonga in Marseille on Sunday, although there is a slim mathematical chance they still might not even make the knock-out phases.

The Springboks ran in seven tries to Tonga's three to nab a crucial bonus point to leave them atop pool B on 15 points.

The two teams who will advance to the quarterfinals will be decided when the world's No 1 ranked team Ireland – who beat the Boks last week – take on Scotland, ranked fifth, in Paris on Saturday.

A win for Ireland would see them finish in top spot and South Africa as runners-up.

However, should Scotland beat Ireland by a margin of 21 points or more, with both teams scoring four tries to earn an attacking bonus point, that would mean all three teams would finish pool play on 15 points.

That permutation would see the Scots topping the group on points difference ahead of Ireland, in second spot thanks to their better head-to-head record against the Boks, in third.

"We'll have to wait," said Boks coach Jacques Nienaber. "Our pool gets sorted out on Saturday so it's a waiting game.

"The key thing for us was to get the win first and then to get a bonus point and then obviously to try to get as many points as we could to put ourselves in the position to get out of our pool."

Nienaber added: "The reality is that where we are currently, I think between ourselves, Ireland and Scotland everybody can still miss out on the quarterfinal, every single team, all three of those teams.

"The pool will only be decided on Saturday."

The Boks had just one job to do against Tonga, a bonus-point victory, and tries from Cobus Reinach, Canan Moodie, Deon Fourie, Jessie Kriel, Willie Le Roux, Marco van Staden and Kwagga Smith ensured that.

POLLARD TICKS BOXES

There was also a welcome return for Handre Pollard after a 13-month absence, the fly-half kicking all four of his conversion attempts.

"It's brilliant to get 50 minutes into his legs, get exposed to international rugby - it's a big stepping stone for him and we can build from there," Nienaber said.

"He got some time in against a proper Tonga side. I think he will get better. He was solid. The fundamentals we wanted him to tick the boxes of, he ticked them."

Bok skipper Siya Kolisi added: "We knew it was going to be a tough game. Hopefully, we've done enough to qualify for the next round."

One casualty for South Africa was a suspected fractured cheekbone for winger Makazole Mapimpi who was forced off after an unfortunate clash of heads with Augustine Pulu that referee Luke Pearce ruled did not merit a yellow card.

Tonga coach Toutai Kefu said he was proud of his team's performance after disappointing opening losses to Ireland (59-16) and Scotland (45-17).

They will wrap up their campaign confident of a first victory of this World Cup against Romania in Lille on 8 October.

"I would have preferred the result!" Kefu said when asked how pleased he was at seeing the team score three tries against the defending World Cup champions, South Africa having previously conceded three over nine matches.

"The boys had a real dig. One of the main things we stressed before the game was putting on a performance that everyone would be proud of and that was one of them.

"That is what rugby is all about. You want to play against the best. That's what makes the good players get out of bed so it was a fantastic experience for everyone today."