The Blue Bulls front row pair suffered injuries in the shock 22-17 loss at Welford Road on Friday night and both players have returned to South Africa.
Hooker Ralepelle, who started the third Test against the Lion four months ago and captained the Boks against the English Champions, picked up a foot injury early in the first half.
And loosehead prop Steenkamp, who also featured in the 28-9 loss to the Lions in Johannesburg, suffered a reoccurrence of a knee injury.
The Cheetahs pair of Adriaan Strauss and Wian du Preez have been called up to replace Ralepelle and Steenkamp respectively.
The Boks also have doubts over tighthead prop Jannie du Plessis ahead of Friday's Test against France in Toulouse, with the Sharks player injuring a hand in Leicester.