With the preseason in full swing, fans and players alike have been introduced to one notable difference in the way the game is played. The league's new helmet rule which prevents players from lowering their heads to initiate contact has drawn plenty of criticism for its unclear nature.

Minnesota Vikings head coach Mike Zimmer is part of the vast majority that is still uncertain about how the call is made. According to Jon Krawczynski of The Athletic, he even went so far as to suggest it could leave some players' careers in jeopardy:

“It’s going to cost some people some jobs,” Zimmer said. “Playoffs, jobs, the whole bit, I guess.

“We haven’t had any called on us so far. It’s just hard to figure out. No one has ever said to me, ‘Hey, don’t worry about it, we’re going to call it less or we’ll get it straightened out in the regular season. Or we’re going to come up with a revised rule.’ No one has ever said that.”

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It is easy to see why Zimmer is concerned about how the rule has been interpreted thus far. Minnesota's defense prides itself on their physicality and the new changes could leave them vulnerable to some heavy penalty yards this season. Their formidable safety tandem in Harrison Smith and Andrew Sendejo will undoubtedly be the biggest casualties of this new rule.

Needless to say, the massive amount of complaints from around the league have not fallen on deaf ears. The NFL is said to be working on a potential solution to help clarify some of the confusion. This could involve the use of a replay to review the calls that are made. Regardless, the league will need to come up with something by the time the start of the regular season rolls around.