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Every week the NFL distributes a video in which head of officiating Al Riveron illustrates some textbook examples of penalties. This week, Riveron started with a blatant example of the penalty for lowering the helmet to initiate contact, from Raiders running back Doug Martin.

And yet Martin wasn’t fined for the foul.

That’s hard to understand: The rule against lowering the helmet is supposed to be a top priority for the NFL this year, and Martin violated that rule in a way that was so obvious the league used it to show everyone else what not to do.

“He now lowers his head, he makes contact with an opponent, he initiates the contact,” Riveron says in the video. “That posture there. Lowering your head, initiating contact with your opponent and making contact, that’s your foul.”

For that foul not to result in a fine is surprising.