Fearless Springbok warrior Deon Fourie says his confidence and fitness are improving game by game and he is ready for any challenges that might be thrown at him during the World Cup knockout phase.

The Boks are facing a tense wait on the sidelines after they wrapped up their group phase of the World Cup with a 49-18 victory over Tonga in Marseille on Sunday, which put them at the top of pool B.

The Springboks have 15 log points after four games and face various permutations depending on the result of Ireland's (14 points) final pool match against Scotland (10) at Stade de France on Saturday (9pm).

With hooker Malcolm Marx ruled out with injury, Fourie — enjoying a new lease of life at 37, the advanced age at which he also played his first game at hooker for the Boks in their 76-0 win against Romania — is a strong candidate to feature in the playoffs if the defending champions get through.

The versatile forward’s typically feisty display against the Tongans earned him the man of the match award.

“Our goal [against Tonga] was a bit bigger for points difference. We didn’t reach that objective, but we’ll see what happens later this week with the big game between Scotland and Ireland,” Fourie said.

“I was way more relaxed than the last two games with my line-out throwing. Romania gave me a bit of confidence and especially Ireland [where he came off the bench in South Africa's 13-8 defeat] with that last throw.

“I know [Bok lock] Marvin Orie from the Stormers, we played two years together, so our synchronisation worked well. I think I lost one line-out against Tonga so that gives me confidence.

“I haven’t played 80 minutes in a long time, so I'll probably do a bit more fitness. I was quite tired on 65 minutes; I didn’t see how I was going to finish this off with 15 minutes to go.”

Fourie said he has been comfortable with his positional switch in France. 

“There’s not much difference between hooker and flanker, apart from the scrumming and line-outs. After that, it’s open play, and [with] how the game’s evolved, you can see how Malcolm Marx plays, he’s almost like a flanker too.”

The Stormers player ranked the clash against the Tongans as one of the most physical he has played in.

“The games in South Africa against the Bulls; that is always physical as well — probably not the [same level of] big hits I felt a few times you saw [against Tonga]. Credit to them, they came out firing.”

Director of rugby Rassie Erasmus said he was comfortable with the Springboks’ log position at the end of the group phase.

“If Scotland beat Ireland by eight points or more and Ireland don’t get a bonus point, then Ireland are out,” he said. “Then, if all three teams finish on 15 log points, the team with the best points difference will go through.

“If Scotland have the best points difference we’ll fall out because Ireland defeated us. But for that to happen, Scotland must score four tries and beat Ireland by more than 20 points and Ireland must also get a bonus point.

“If Ireland have the best points difference we’ll go through because we defeated Scotland.

“From our point of view, we did what we had to do to go through and we now have time to prepare for the different scenarios. Some of us will prepare for the All Blacks, and others for France.

“But France and Italy still have to play, so we’ll have guys preparing for Italy too. Italy are used to facing the northern hemisphere teams, so there are still interesting permutations.”