Miller wouldn't be a backup.
And you can't ever, never ever ever project a finish based on two individuals just like that. That has zero accuracy to it. And if needed, Lack might very well be ready to be number one. This would just give us more safety on that matter and help him further develop. He's been playing hockey for quite some thine now, so responsibilities are not new to him. He's been the starter on many teams, on many levels for several years now.
I'm out eating lunch right as we speak. And I'm just not anything, I'm someone.