The Blitzboks finished day one at the Singapore Sevens with a hard-fought 26-12 victory over Argentina on Saturday.
Earlier in the day, the South Africans beat Samoa 26-5 and Canada 26-12.
They will now face Kenya in the Cup quarter-final on Sunday (6.52am SA time).
Werner Kok was instrumental in the win over Argentina, flinging a long pass out to Siviwe Soyizwapi to score, and then putting his foot down himself to scamper over.
Neil Powell and his team may have thought that it was an easy saunter in their last game on day one, but things turned quickly before the halftime break.
First Tomas Passaro found his way to the tryline for Argentina, and then Lautaro Bazan Velez levelled the scores at 12-12 with a touchdown and conversion.
Powell spoke urgently at the break, and it had the desired result. Stedman Gans cut the Los Pumas defence before the quicksilver Selvyn Davids eventually sped away from a ruck to dart over.
Davids was again the spark for the final try as he put in a well-weighted grubber that was chased down by Muller du Plessis, who hacked the ball forward and raced through to fall on the ball.
But the Blitzboks will tackle their quarter-final without Rosko Specman (dislocated shoulder), while captain Kyle Brown was stretchered off after a knee injury and will miss the rest of the tournament.
Blitzboks 26 – Tries: Siviwe Soyizwapi, Werner Kok, Selvyn Davids, Muller du Plessis. Conversions: Selvyn Davids (3).
Argentina 12 – Tries: Tomas Passaro, Lautaro Bazan Velez. Conversion: Velez (1).