There are teams noted for being really good during the regular season, but as the playoffs near they begin to falter. And then should they get into the playoffs, they exit rather early. This was the Rams story for years and years.
The Lions are, at least this year, seemingly one of those teams. And, I think the Cowboys are as well. I expect both to make early exits from the playoffs.
I think today's test against the Giants is bigger than their final game against the Niners. If the Rams win today, they are in the playoffs unless some crazy series of events involving ties and other stuff happens (from what I read). They know this. If they lose, then it says they are not quite there yet.