Originally Saint-Andre had named 24 players, cutting down from the final 33, due to uncertainty surrounding the fitness of several back-row forwards, most notably Louis Picamoles and Fulgence Ouedraogo.
But with both resuming full training, flanker Nyanga was the unlucky man and will return to Toulouse, despite having played all three Tests in November.
There is also a spot for former captain Thierry Dusautoir, who makes up the back-row quartet with Damien Chouly, but Saint-Andre hopes Nyanga is back with the squad in the near future.
"It is heartbreaking to have to tell Yannick [Nyanga] that he has to leave," said Saint-Andre.
"He is a great competitor who drags the team up with his demands and also brings his good spirit and joy of being in the group.
"He's had a great week of work but that's the top level, healthy competition and choices that give the selectors a headache.
"We will continue to monitor him and I hope he is back with us soon."