The Rams OBVIOUSLY lost because there were ZERO jet sweeps to Tavon. Run that play once and the Rams win by 10 points.
I think they lost because the Rams couldn't beat man coverage. This allow Atlanta to focus on taking away Gurley in both the running and the passing game, which they did for 3 quarters.
And two TOs on special teams in the first quarter was far too much to overcome. I do think that sort of rattled this young team.
IMHO, it has nothing to do with who played and who didn't play vs. SF. Though I would consider this... Would the extra time taken, if any, for the coaches to prepare the 2nd stringers to play vs. SF have been better spent game planning for Atlanta?