A popular conversation coming out of the NFL preseason surrounds the league's new use of the helmet rule and what effect it will have on scoring, specifically for those of us trying to make sense of over/under betting.
Theoretically, more penalties — specifically the 15-yard variety — for illegal tackles will significantly benefit offenses and therefore result in more points scored.
In sports betting circles, the key question is whether the new helmet rule will, in fact, result in higher-scoring games, especially early in the season as oddsmakers are forced to adjust on the fly.
In Week 1 of the NFL preseason, 11 of 16 games went over Pinnacle's closing total, forcing oddsmakers to react in Week 2, which they did, resulting in unders going 10-6.
Unders finished 10-6 again in preseason Week 3, with average points per game plummeting to 35.81, down from 41.63 points in Week 2.
Overs bounced back in Week 4, going 10-6 and finishing the NFL preseason at 33-32, including the Hall of Fame Game.
There is a narrative that officials are more aggressive with recent rule-change penalties in the preseason but tend to back off and take a more conservative approach once regular-season action begins.
I reached out to Geoff Schwartz, a former NFL offensive lineman and current football analyst at The Action Network, and asked him this question: Following offseason rule changes, are NFL officials more willing to throw flags in the preseason than after the regular season begins?
"That's 100% accurate," Schwartz replied. "They will over-call new rules in the preseason, then should slow it down once the season starts."
According to a report from ESPN's Kevin Seifert, a combined 20 flags for players illegally lowering their helmets were thrown in Weeks 3 and 4 of the NFL preseason, a 60% reduction compared to Weeks 1 and 2.
While there's no way of truly knowing how aggressive referees will be with this specific rule, we can look at past Week 1 over/unders to determine how this year's totals compare to previous seasons.
Using Bet Labs' historical NFL betting data, I pulled average closing totals for every Week 1 matchup since 2008, then organized them by season for comparison.
NFL closing Week 1 over/unders
Week 1 of the 2008 season offered the lowest average closing total of the past 10 years at 40.97. After bouncing between 41 and 43 the next three seasons, over/unders spiked up to 43.94 in 2012 and again to 45.59 the following season.
In 2011, the average Week 1 over/under was 41.16 compared to 47 points scored per game. As a result, opening-week over/unders rocketed to 43.94 in 2012 as oddsmakers adjusted for the scoring spike from the previous season.
Once again, offenses went nuts, scoring an average of 49.44 points per game in Week 1 of 2012. Oddsmakers reacted drastically again, evidenced by an average Week 1 total of 45.59 in 2013.
Since crossing 45 in 2013, the average Week 1 over/under has yet to drop below that number in any season since. The average Week 1 total for 2018 is 45.63, which would tie 2014 for the highest in our sample.
Please note that 2018 over/unders are still available for betting, so this number can change between now and the close of all Week 1 action.
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So this begs the question: Is the increase in over/unders compared to the past three seasons due to the NFL's helmet rule?
Well, we can't blatantly say it's because oddsmakers are expecting more points, but I believe the increase is due to the perception of the new rule among fans and mainstream sports media.
In each of the past four seasons, the average points scored in Week 1 games has fallen below closing totals.
NFL Week 1 over/unders vs. points per game
Interestingly, average points scored per game (40.40) finished considerably below average closing totals (45.57) last year.
In fact, 126 Week 1 games have been played since 2014 (Buccaneers-Dolphins was postponed in 2017 due to Hurricane Irma) and 63 of those finished under, while 63 have gone over the closing totals.
In short, closing totals have been basically perfect over the past four seasons.
With four straight years of Week 1 scoring falling below closing totals, including the massive 5.17-point difference in 2017, and over/unders splitting exactly 50/50, there's no reason for 2018's totals to increase, at least when you base it on historical betting data.
In addition, NFL teams averaged 21.7 points per game in 2017, the lowest total since 2009. So the increase in Week 1 totals isn't a reaction to a general increase in scoring from last season either.
It might not be due to the new helmet rule, but it appears that perception is driving up Week 1 over/unders, especially considering recent scoring trends and if we presume that officials will remain conservative with flags once the regular season kicks off.
Unders are 111-94-2 (54.1%) in Week 1 since the start of the 2005 season, something to keep in mind when breaking down opening week over/unders.
