If you look back over the season, I think something that stands out is that the Saints have problems with teams that are balanced, and play well vs teams w/o balance. They struggle vs the run against teams that are a threat to throw.
San Fran is pretty one dimentional, and wont cause a young saints defense to guess as much. They shouldn't give the saints the kind of problems that the dallas offense will with thier balanced attack. Sounds simple, but it is something that I believe.