Easy call IMO... The multitude of bad reviews were already up on Rotten Tomatoes on Thursday -- this movie was getting bashed by everyone.
So it basically came down to looking at comparable movies... Horror/suspense with a decent star (but certainly not a star people flock to go see), not marketed towards the teen crowd (like Texas Chainsaw Massacre was), preview wasn't that great... My comparable movies:
Stigmata, Identity, House of 1000 Corpses, Stir of Echoes, Frailty, In Dreams... All under $14 million.