Mpupha is following head injury assessment (HIA) protocols, which means she will only be able to return to the field next Monday, while Janse van Rensburg suffered a groin injury in Dubai and will not recover in time to play.
Mpupha took a knock in their match against Japan on Sunday, while Janse van Rensburg did not play at all on the second day of the Emirates Dubai Sevens, where South Africa finished in 10th position.
Their replacements will be named on Thursday.
Springbok Women's Sevens assistant coach Cecil Afrika said the ability of both players to remain calm under pressure, as well as their physicality, will be missed.
"It’s a loss for us, but injuries happen, and we need to adapt,” said Afrika.
“We lost Eloise Webb prior to Dubai and still delivered a proud performance. Two new players will now get the chance to make the step-up and stake a claim. Someone else needs to step up and take over in their positions.”
The South Africans came within seven points of both New Zealand and Fiji in Dubai, and given the average scoreline of 40-0 against New Zealand in all previous matches and the 59-0 drubbing Fiji handed them in their last encounter, the Springbok Women’s Sevens showed a vast improvement, but for Afrika, there is still more work ahead for the team.
“It’s actually more fine-tuning than changing anything for us this week,” Afrika said after the team’s training session at UCT on Tuesday.
“We’ll get better as we go along and pick up experience. We came so close, but our decision making under fatigue was a problem.”
Afrika added the team will look to secure their breakdowns more effectively as well this weekend.
“We need to protect our ball a bit better and have more patience on attack,” Afrika said. “We create the opportunities, but don’t always finish them. We are still learning, and will make better decisions. It’s part of growing pains.”
Commenting on their solid defensive effort in Dubai, the assistant praised the team’s commitment and attitude.
“Defence is not a talent thing, it’s work ethic and attitude, and the team has plenty of that,” he said. “It’s all about the system and we prepared well in our analysis, which worked in our favour. We just need to work smarter, not harder on defence."
Afrika said the next challenge for the team will be to get straight back into action, despite their aching bodies.
“We have home ground advantage - something no other team will have,” he said. “The squad will be reminded of our vision and goals for the season and also what we want to achieve in our home tournament. Then we’ll be good to go again.”
South Africa will line up against Canada, France, and USA in the pool stages on Saturday.