Nearly every week between August and February, the NFL picks a handful of officiating calls to highlight in an online media video. The first installment, distributed last Friday, led off not with the much-talked-about pass interference reviews, but rather with two examples of the helmet rule in action during the Aug. 1 Hall of Fame game.

The first instance went uncalled by officials on the field. The second, according to senior vice president of officiating Al Riveron, was flagged incorrectly.

With public attention focused on the recent addition of pass interference to replay review, the NFL is still trying to figure out how to administer it after last year's officiating debacle. The helmet rule -- prohibiting players from lowering their helmets to initiate contact with an opponent -- is one of two points of emphasis for 2019, meaning officials have been asked to pay special attention to it. There is an expectation that it will be enforced more tightly on the field, but the difficulty involved with fulfilling that task makes the helmet rule one of the most enigmatic NFL edicts in recent memory.

"There's an adjustment period involved, and everyone knows it," said competition committee chairman Rich McKay. "These players didn't play with this rule for a long time, meaning their entire career. There's an adjustment period for on-field officials. We're confident that ... they are going to get better at it as they look for it more. But at the same time, we're confident that we're going to see less of these fouls because players are going to be more comfortable with it."

The NFL wrote off traditional enforcement of the rule in its 2018 debut, an unprecedented decision that led to only 19 flags in 256 games. The league did, however, issue 28 fines and 139 warning letters to players who had in most cases committed fouls that went uncalled. That discrepancy, while preferable to a flood of penalties, called into question the integrity of the game and prompted fair questions about whether the rule was simply unenforceable lip service to the league's health and safety apparatus.

The 2019 season should answer those concerns, one way or the other. Officials were given an offseason study guide to help them identify violations "to better recognize when players initiate helmet contact," referee Adrian Hill said. Players and coaches, meanwhile, have heard the mantra now for 15 months.

In this week's video, Al Riveron explains Use of the Helmet (UOH) - a foul that occurs if a player lowers his head to initiate and make contact with his helmet against an opponent. For the full explanation, visit: https://t.co/2C6En79afN. pic.twitter.com/bUJmXfBrTv

— NFL Officiating () August 9, 2019

"It's a violent game," said Chicago Bears coach Matt Nagy, "but we as coaches have to be able to teach tackling the right way, and that's keeping your head and helmet up."

But the annual flood of young players into the league demands constant vigilance and reiteration; the helmet rule is different from anything at any other level of football. Players have always been coached to hit with their heads up but were never penalized if they didn't and thus had little on-field incentive to avoid lowering the helmet.

When the rule was announced, many players predicted there would be instances when lowering the helmet was unavoidable. The NFL initiated a universal rules alignment initiative last season, designed to introduce similar rules from Pop Warner through high school and college, but it will be years before those efforts manifest in players entering the NFL.

In the meantime, we could continue to see plays such as those highlighted in last week's NFL video. In the first, Denver Broncos safety Will Parks lowered his helmet and hit Atlanta Falcons running back Brian Hill in the hip with his helmet. The contact, which took place in the middle of the line and was clearly visible only from an end zone view, went unpenalized.

The second instance was more obvious but still went incorrectly adjudicated. Referee Walt Anderson's crew flagged Hill for lowering his helmet to hit Broncos safety Dymonte Thomas after a run down the right sideline. Riveron said the call on Hill was correct, but demonstrated that Thomas also had lowered his head to initiate contact and should have been penalized as well.

There was a total of five flags thrown for violations of the helmet rule in the first 17 games of the preseason -- a much slower pace than the chaotic 2018 preseason, but more than the average of 1.1 per week during the regular season. The continued focus, however, is not simply a means to align enforcement with behavior. The NFL also believes that the mere introduction of the rule changed behavior in 2018.

According to league data, concussions involving a player who lowered his head to initiate contact decreased by 20% in 2018 compared to 2017. A player lowering his head was still involved in about 50% of all concussions from helmet-to-helmet contact, and overall, 40% of all concussions still involved some kind of helmet-to-helmet contact in 2018.

"That is one data point and it is one year," said Jeff Miller, the NFL's executive vice president of health and safety initiatives. "That is not a lot of information. [But] helmet-to-helmet contact causing concussions, that number is 20% lower than it was a year ago. So that is positive thing. There's obviously a lot more to do in that space. That is something that was very interesting to the competition committee as they continue to push and make an emphasis on this point. So that is a teaching point, a player-adoption point, a culture-change point, and a good one."

The NFL's efforts in this space have tested its ability to leverage a legitimate safety initiative against behavior that is genuinely difficult to change with a rule that is objectively hard to officiate. The league essentially punted on the first season and is taking a long-term approach. But how many years will it take to get there? Progress in 2019, defined by more appropriate officiating, is essential to getting there.