Why Can't Marshall Get A Chance In The College Football Playoff?

The top three teams in the College Football Playoff seem pretty well locked in, so long as they take care of business down the stretch. Those teams would be Alabama, Oregon and Florida State. Right now, Mississippi State has a hold of the 4-spot, with TCU, Baylor and Ohio State giving chase. But why can’t undefeated Marshall get the opportunity for this final berth in the College Football Playoff?