Dan Campbell says a little of both.
Rookie DBs made some mistakes, including Rakestraw, who cost the team great field position by knocking a perfect punt into the end zone. Offense was largely out of sync, except Montgomery and Jamo.
People are underestimating the Rams. Remember this is the franchise where Holmes learned to be a great evaluator of talent. They won a SB, had a terrible season after Stafford got hurt, then gave Detroit a run in the playoffs last year. Yes Aaron Donald retired and they had injuries but are a good team with good players, good coaching, and a great QB.