If Peters plays then the belief is that he is ready enough and cannot hurt himself worse.
The Rams aren't stupid. They're not going to ruin a young elite corner for the sake of 1 or 2 games. Nor are they going to not give him time to heal now, so that as they enter late November and December that the team isn't as healthy as it can be.
Besides, while Hill and Shields aren't Talib and Peters, they more than held their own against a desperate Chargers when they're only choice was to pass the ball. Both CBs are fast and experienced. It's not like the cupboard is bare.