If you still believe that its the Vince Lombardi era where players fear the coach, then you're right. However, it is not the 1960s anymore and these mega-rich players that are protected by their union so they cannot be forced to take a hit in practice, are not going to be intimidated into playing hard-nosed, disciplined football for 60-minutes.
The only way you can get them to perform is when they're playing for each other. McDermott has the right idea in team building in the 21st century. But, he simply cannot whip them into shape.