Will Cain asks why NFL teams are so focused on hiring offensive-minded coaches instead of coaches similar to Bill Belichick. (1:23)

Perhaps you remember the offensive explosion of 2018. Teams were scoring at a record pace, mostly because of highly efficient passing attacks and a reimagined role for running backs.

The NFL rejoiced and the television ratings went up and the world was saved until ... it all hit a wall in Week 14.

In a little-discussed epilogue, the 2018 breakthrough softened considerably in the final four weeks of the season. Pace slowed across the board, leaving most NFL records intact and prompting questions about what it means for 2019. Did defensive coaches and schemes catch up? What about factors like injuries and weather, long cited by coaches as impediments to late-season offensive efficiency? And will the league rebound in 2019?

Fans of offensive innovation should rejoice in knowing that six of the league's seven new head coaches come from offensive backgrounds. Their arrival raises the total of coaches who will call their own plays to 17, an increase of 21% from 2018 as teams focus on offense from the top down. But on the other hand, none of the NFL's 2019 rule changes or points of emphasis favor the offense, and a few could actually make it more difficult to move the ball early in the regular season.

Let's take a closer look at the NFL's offensive landscape as the regular season approaches, utilizing special research by ESPN senior statistics analyst Jacob Nitzberg.

Rules rebalanced for 2019

Shadows of 1978 hovered over the majority of the 2018 season. It had been 40 years since the NFL instituted illegal contact as a foul, prohibiting defenders from significant contact with receivers beyond five yards from the line of scrimmage and launching an intentional favoring of offense over defense for aesthetic purposes.

In 2018, the NFL competition committee juiced the game once again when it made illegal contact and roughing the passer points of emphasis for officials, resulting in a spike of both penalties during the first five weeks of the season. Players adjusted by reducing contact with receivers and softening their pass rush. And when they didn't, opponents were given free yards and extra first downs via penalties. Both outcomes aided offenses for the first 13 weeks of the season, competition committee members agreed at the time.

In 2019, there are two significant rule changes and two points of emphasis. None are expected to provide the boost that offenses received in 2018.

Reviewing pass interference will allow senior vice president of officiating Al Riveron to add a penalty to what had originally been a no-call. But those penalties could be against the offense or defense. Riveron has warned about the possibility of seeing and calling offensive pass interference on a review of a defensive penalty. In fact, according to an internal study the NFL performed during the offseason, the most frequent penalty type among the 50 biggest non-calls of the 2018 season (based on win probability) was offensive pass interference.

The other major rule change is a prohibition of all blindside blocks. The adjustment was made primarily to improve safety on punts, but it will also apply to offensive linemen (and any other players) who are moving toward their own goal line while blocking. When you combine that rule with a point of emphasis on backside offensive holding, you can make an argument that the NFL has made it more difficult to block effectively.

Along with holding, the NFL's other point of emphasis for this season is a more substantial enforcement of the helmet rule, which prohibits players from lowering their heads to initiate contact with an opponent. Part of the emphasis is encouraging officials to identify and call, yes, offensive players -- especially running backs -- who use that posture. In 2018, only one offensive player was among the 19 players flagged for the foul.

The late slowdown of 2018

We outlined the 2018 explosion of offense after Week 13, attributing the surge to five primary factors beyond the rule changes:

Increased comfort in spread concepts, especially with moving the quarterback out of the pocket

Passing more frequently on first down, increasing average yards and leading to fewer third-down plays

More common use of three-receivers as a base set, with unprecedented effectiveness over the middle

More effective use of running backs in the passing game

More elite quarterbacks

But almost immediately thereafter, those trends slowed or reversed. Most notable was a sharp reduction in success on passes over the middle. League-wide QBR dropped from 85.9 on such throws in Weeks 1-13 to 77.9. And running backs were less productive in the passing game, accounting for a full yard less after the catch in Weeks 14-17.

As a result, scoring dropped 14% on a per-game average during the final four weeks of the season. Yardage fell 7.8%, and passing touchdowns occurred 21.4% less frequently.

So what happened? Coaches surveyed this summer cited several traditional explanations, noting that offense historically slows in December as weather worsens and injuries mount. Indeed, teams placed more players on injured reserve in Weeks 14-17 than in any other four-week span, and those numbers skewed more toward offensive players.

The Los Angeles Rams, dealing with running back Todd Gurley's late-season knee condition and the loss of receiver Cooper Kupp, scored fewer than 23 points in two of their final four games. They had surpassed 30 points in 11 of their first 12. The Kansas City Chiefs, playing without running back Kareem Hunt, saw their points per game average drop 18%, from 37.0 to 30.3.

However, it is impossible to ignore the sharp reduction in flags for illegal contact and roughing the passer compared to the first five weeks of the season. The NFL often uses the early portion of the season to set a tone on new rules and emphases, after which both players and officials adjust into a less disruptive flow. By the time Week 14 arrived, illegal contact flags were down 45% and roughing the passer penalties had fallen by 30%.

Meanwhile, the NFL issued a one-week emphasis on offensive holding in Week 13, leading to by far the largest total of holding penalties for any week since ESPN Stats & Information began tracking it in 2012. Was it pure coincidence that NFL offenses slowed down just as the league had made pass defense easier and pass protection more difficult?

Implications for 2019

What do teams have in store for a "non-juiced" NFL season? Much of last season's offensive spike was the culmination of longer-term trends. Comfort in the spread, primary use of three-receivers and maximizing the value of pass-catching running backs should continue to provide the foundation of offenses in 2019.

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The model for annual innovation is in Kansas City, where Chiefs coach Andy Reid can always be counted on to pop a new concept into the NFL lexicon. One of his proteges is in Chicago. Bears coach Matt Nagy smiled this summer when asked if he spent the offseason racing Reid toward innovation.

"I know he's doing it," Nagy said. "I grew up learning that from him, and I know that we and everyone else are trying to do our own things, as well."

One area for growth is the continued assimilation of "trick plays" into every-down offenses. Sixteen quarterbacks caught a pass in 2018, the most since the 1970 NFL-AFL merger. A total of 36 non-quarterbacks threw a pass, with 24 completing each one. And there were 13 touchdown passes by non-quarterbacks, the most since 1983, according to the Elias Sports Bureau.

A subset of that trend is an intensified interest in players such as New Orleans Saints quarterback Taysom Hill, who developed into an all-around playmaker even with starter Drew Brees on the field. At least two quarterbacks were drafted with that potential purpose in mind -- the Baltimore Ravens' Trace McSorley and the Los Angeles Chargers' Easton Stick -- and the New England Patriots experimented with quarterback Danny Etling as a receiver before releasing him earlier this month.

"It seems like there are more and more teams who are more open-minded to go that route," said Green Bay Packers coach Matt LaFleur. "Having a utility man like that can be such a threat."

The key to using such a player, whether in a wildcat formation or even in the backfield along with the starting quarterback, is the legitimate possibility that he could throw. That twist prevents defenses from bringing an extra defender to the line of scrimmage.

"These teams like to do that when you pull a non-thrower back there," Nagy said. "But if you do that, there's no help deep. So if you have a guy that can throw, it's either one-on-one coverage or they have to put that extra guy back, and that makes it easier to run."

There is every reason to think that NFL offensive innovation will continue, especially given the background of the majority of new head coaches. And should it go awry, and games get muddled in punts and penalties, the NFL has ways to adjust and intercede as needed.

In 2018, for instance, the competition committee clarified the roughing-the-passer emphasis last September in a way that eventually dropped penalty totals. The slowdown of illegal contact flags, and the one-week uptick for offensive holding, represent additional examples.

But if the numbers rise notably again in 2019, a year when the league has not particularly greased the rails for offenses, one conclusion will be certain: Teams will have earned it.