Lucu was shown a yellow card for a high tackle of his own. He was only just back on the field when Grandidier-Nkanang was sent off too, after he slapped down a pass in the French 22.
South Africa's power then told. The world champions scored their opening try from a maul, before Erasmus changed his entire front row again, five minutes before half-time.
The margin was only two points. France were hanging on by the fingertips for the final 30 minutes, but they at last beat the best team in the world at home.
In those 21 years the side had turned through successive generations and multiple iterations, rising, falling and rising again.
The match took its first turn after 10 minutes of frantic tussle, when Lood de Jager was sent to the sin-bin for a high tackle.
It was an odd decision. South Africa had been dominant in the scrum.
All of a sudden a French bench featuring three front-row replacements, with 25 international caps between them, faced the prospect of packing down against the gnarliest front row in international rugby.
Galthié had said Dupont was going to start at fly-half. He wore No 10, but he played the game in his usual position.
Despite losing Wiese to a 20-minute red card early in the second half, the world champions took advantage of Grandidier-Nkanang's sin-bin for a deliberate knock-on.
South Africa finally burst through, but the ball was held up.
Tiredness and poor discipline made the game loose and chaotic, before the Springboks turned to their scrum to regain control.
Despite their scrum crumbling, France held firm, continuing to chase kicks and compete for loose balls.
Stunning scramble defence and sheer grit showed a side of the back-to-back Six Nations champions that has often been questioned.