South Africa centre Lukhanyo Am has replaced injured wing Makazole Mapimpi in their World Cup squad.

"It's sad that something like that happened. It was an accident," South Africa director of rugby Rassie Erasmus said Mapimpi's injury.

South Africa have completed their Pool B fixtures and sit top - but could still go out depending on the result between Scotland and Ireland.

Should the reigning champions progress to the quarter-finals, Erasmus has called up 2019 World Cup winner Am, who made the assist for Mapimpi's try in the final against England four years ago.

Erasmus said Mapimpi will be out for between four and six weeks.

"We will not just miss him as a brilliant rugby player but what he brings to the team. There is a lot of heart, a lot of honesty," Erasmus said.

"He doesn't say a lot - but when he says something, everybody listens. He trains hard, communicates beautifully on the field while he is really quiet off the field. He never moans if he is not selected and helps the young boys who get selected.

"If we get to the final, we will definitely fly him back to join the rest of us here. The same with the other guys who got injuries and went back to South Africa. It's sad but that's the game of rugby. Those collisions happen."

'Tough call' between Pollard and Libbok

With South Africa having played their four group games, Scotland face Ireland and Tonga take on Romania in the final round of Pool B fixtures this weekend.

The Springboks beat Scotland 18-3 in their match in Marseille, with further wins against Romania and Tonga, but were defeated by Ireland.

Questions linger over squad selection for a potential quarter-final against France or New Zealand, in particular at fly-half after Handre Pollard and Manie Libbok both had good games against Tonga.

Pollard replaced hooker Malcolm Marx, who suffered a knee injury, in their squad earlier in the tournament, but Erasmus indicated that Libbok is ahead of him.

"Unfortunately for Handre, it's only the one game he has played," Erasmus said. "Manie had proved himself the way he has played in general play for us. Handre made four kicks and Manie three kicks, so we kicked seven out of seven [against Tonga]. It's a tough call we will have to make."

'I'd rather sit here than be Ireland'

Because of the fixture schedule, South Africa are in the odd position of preparing for a quarter-final they are still not sure they have reached.

Scotland side need to beat Ireland and deny Andy Farrell's team a bonus point in Paris next Saturday to qualify. If they manage that, the Springboks will top the pool.

However, a combination of a bonus-point win for Scotland and a losing bonus point for Ireland will leave all three sides on 15 points, meaning it will come down to points difference for the top spot and head-to-head for the second spot.

But Erasmus says he prefers to be in their current situation rather than being one of the teams still needing to play.

"With full humbleness, and there is no arrogance saying this, but I'd rather sit here than be Ireland knowing that we've been number one in the world all the time and Scotland basically just have to beat them by eight points and they are out of the tournament," he said.

"The score could be 22-12 or 22-13 and Ireland are out of the competition if they don't get a bonus point. Of the three teams, we are probably the most comfortable sitting here knowing we have got a two-week rest.

"Look, maybe we have got six months rest if the cards don't fall our way."