The flyhalf was forced off in the Stormers' 44-21 United Rugby Championship quarter-final victory over Cardiff on Saturday.
Reports suggest that Feinberg-Mngomezulu has suffered a high ankle sprain which could keep him on the sidelines for the next three months.
That would rule him out of the rest of the Stormers' season and the early part of the Springboks' Test campaign.
They face England, Scotland and Wales in the Nations Championship before their huge set of matches against the All Blacks in the Greatest Rivalry tour.
Should that prognosis be accurate, the playmaker would at the very least miss a part of that series.
"That's rugby and that's why Rassie works so hard to make sure there's a lot of depth and there are people that can step in," an unconcerned Matfield said on the Rivals podcast alongside All Blacks great Sir John Kirwan.
"It's not bad to have Handre Pollard or Manie Libbok come in for Sacha, that helps quite a bit. Handre is playing fantastic rugby for the Bulls at the moment.
"It's still a year out from the World Cup so I would rather take all the injuries this year than next year."
A surprised Kirwan duly queried Matfield's stance, asking: "You're not worried about the All Blacks, Victor?" But the former South Africa lock doubled down, responding: "Do we need to be?"
The focus then turned to the scrum-half position where Kirwan was left hugely impressed by the performance of Embrose Papier.
After a stunning season for the Bulls, Papier was named in the Springboks' alignment camp recently and, given the injuries in the nine position, could well play a key part for Erasmus' side.
"Embrose Papier has been outstanding the whole year. There was quite a lot of unhappiness with the first two alignment camps when he wasn't there," Matfield said.
"Everyone said: 'How can he not be there?' He's probably the number one scrumhalf in South Africa at the moment.
"If you look at scrumhalf, Grant Williams is out, Jaden Hendrikse is out, Krappies (Morne van den Berg) is out, Cobus Reinach is out, so the top-four are all out.
"But Embrose is playing such great rugby. He played for the Springboks four or five years ago, he went through a dip, but this last season he's been outstanding.
"He's been scoring tries from everywhere, his kicking game is on point and he's always dangerous around the ruck.
"I think he's the second-fastest they've measured this year so he's got a lot of speed."
Bafana Bafana legend Sibusiso Zuma has questioned how several players were told they would not make South Africa's 2026 FIFA World Cup squad, saying head coach Hugo Broos could have handled it better.
Banyana Banyana were given a harsh reminder of the standards required at the highest level of women's football after suffering a heavy 5-0 defeat to Japan in the first of two international friendlies at Yanmar Stadium in Osaka on Saturday.
Springbok flyhalf Handre Pollard has no doubt that this year's Greatest Rivalry series against the All Blacks is sure to be something truly special.
Ivan van Rooyen and Sacha Feinberg-Mngomezulu have added their names to the United Rugby Championship Awards roll of honour by collecting the Coach of the Season and Players' Player of the Season titles.
