I'll agree mobility is a good thing for a QB to have but when it's all they have it becomes a problem. The NFL also isn't college where QBs regularly rush for 1500 yards and 20 TDs. QBs have to be able to throw first and use the mobility as an additional threat. Maybe Fields proves me and everyone else that sees him as a run first guy wrong... But right now, I don't think he scares teams with his arm.