The producers search for a co-lead who can match Shailene Woodley’s talents:
She has real power and they seem weak next to her. After Tris, this is the most essential piece of casting in the movie. Four has to have mystery. He has to have charisma. He has to be old-fashioned manly or the story’s not going to work. .. One actor had “pretty good chemistry with Shai.” Another guy is “a real Australian hunk with a perfect American accent, but he looks old standing next to her.” And all these actors were about to get big leads in other movies. They just weren’t Four.