Mollema's reaction says enough. He said Froome and Porte weren't really riding away fast from the group. He was too far back to react initially but when he saw they weren't pulling away so hard, he attacked and joined.
If Quintana can't follow a Froome clearly not in ultimate form.. then that's worrying.
If Quintana can't follow a Froome clearly not in ultimate form.. then that's worrying.