NFL officials threw 4,057 flags during the 2018 regular season. That number should sound familiar to close observers.

Their total was 4,044 last season. And 4,048 in 2016. And 4,180 in 2015. And 4,093 in 2014.

The past five years have brought a crazy -- and maybe not so organic -- level of consistency to penalty frequency in the NFL. But uniformity in the aggregate has masked substantial deviations among crews, data that every team studies during game preparations.

The league seeks to minimize those trends in the playoffs by breaking up crews and mixing them in part by performance and experience. As the 2018 postseason approaches, however, there are still some relevant inferences to make in our annual officiating scouting report. Let's take a look at the tendencies of each crew from the 2018 NFL season.

Note: All data includes penalties that were accepted, declined and/or offset. Penalty numbers are from ESPN Stats & Information.

Conference championship assignments

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Overall frequency

Simply put, some crews will throw more flags than others. But in 2018, the gap was a bit more notable than usual.

Referee Shawn Hochuli's crew threw 55.7 percent more flags per game (20.4) than referee Bill Vinovich's crew (13.1). (For comparison, the top-to-bottom gap was about 50 percent in 2017.) Hochuli was averaging more than 21 flags per game for most of the season, until his crew threw a season-low eight in Week 17, a Kansas City Chiefs 35-3 blowout of the Oakland Raiders.

Although full historical data isn't available, retired referee Terry McAulay (now an NBC Sports analyst) said he could not remember a larger gap between the top and bottom of the 17 crews covering the majority of the season.

McAulay theorized that this season's numbers were exacerbated by an assignment structure that broke from NFL norms. In essence, it looked to minimize the use of the league's four rookie referees -- including Hochuli -- in the most important games of the year. As a result, Vinovich -- in his 10th season as a referee -- worked six Sunday Night Football games.

"Certainly, some of that has to do with the fact that the crew that threw the least was working the teams that are the best," McAulay said. "And historically, with rare exception, those teams commit fewer penalties. And the crew that has got the most is one of the rookie referees, and they're clearly not working the teams that play the best."

Indeed, four of the eight crews who threw the most flags were led by rookie referees. In previous years, the NFL has not assigned rookie referees to postseason games. That increases the likelihood of staffing the playoffs with referees whose regular-season crews have thrown fewer flags.

Roughing the passer

Because postseason crews are mixed, there is marginal value in studying a referee's regular-season trends. There are a couple of exceptions, however. The most notable is roughing the passer, because the referee is the primary official tasked with watching the pocket and throwing flags on fouls involving the quarterback.

As the chart shows, the wild-card round will feature two of the five referees who threw at least 10 flags for roughing the passer this season: Walt Anderson and Clete Blakeman. Vinovich called two such penalties, an NFL low.

Roughing the passer was one of the biggest stories in the NFL during the early part of the season. There were 31 flags thrown in the first three weeks to accommodate a point of emphasis against landing on quarterbacks with full body weight. A competition committee clarification prior to Week 4 scaled back the frequency for a while, but the point of emphasis had its effect.

There were a total of 119 roughing the passer calls for the season, 10 more than last season and 27 more than 2016.

Offensive holding

Referees also are tasked with watching offensive tackles as the play begins, making it worthwhile to examine offensive holding data. And this topic is especially relevant for 2018.

Offensive holding was the most common penalty (3.4 per game) and accounted for the most penalty yards (26.9 per game). It also was the source of one of the most bizarre moments of the season: A one-week, 42 percent spike in holding calls during Week 13.

Hochuli's crew called 10 holding fouls that week. Jerome Boger's crew called nine, and John Parry's crew called eight. The season totals were topped by Hochuli. Vinovich called the fewest (27), while veterans John Hussey, Tony Corrente, Walt Coleman and Brad Allen all threw fewer than 40.

Even though Hochuli is not expected to work a playoff game, it's worth taking a step back and understanding that one crew (Hochuli) called nearly three times as many holding fouls as another (Vinovich) in the same number of games. That's a wild level of variation.

Pre-snap movement

Watching for false starts, encroachment and neutral-zone infractions primarily falls under the down judge, line judge and umpire. It seems straightforward. An offensive player can't make sudden movement before the snap once he is in a set position. A defensive player can't be on the other side of the line of scrimmage at the snap.

This season, however, inconsistency on what should be a standard call has led to dramatic consequences. One of the most notable missed calls was early movement in Week 6 by Los Angeles Chargers left tackle Russell Okung on what turned out to be a scoring play. The official who missed it was down judge Hugo Cruz, whom the NFL fired for performance reasons in October.

What's notable about this season's pre-snap data is that Vinovich's crew tied Hochuli's for the most false start penalties (43). Parry's crew, on the other hand, called 23. Those numbers are worth remembering in the playoffs as referees sometimes set the tone for penalty enforcement beyond the areas they are specifically assigned to.

Offensive tackles who use an early leg kick to prepare for a pass rush might have a better chance of getting away with it in a game worked by Parry than Vinovich. Full pre-snap numbers are in the chart below:

Pass defense

Illegal contact was a 2018 point of emphasis and probably contributed to an elevation in passing efficiency by most offenses. Calls nearly doubled from 2017, from 38 to 70. There also was a slight increase in defensive holding calls, from 303 to 328, but a sizable decrease in defensive pass interference (303 to 265) maintained almost the exact same level of total calls on defensive backs during passing plays.

There were 660 penalties for defensive pass interference, defensive holding and illegal contact in 2017, and 663 in 2018.

Walt Coleman's crew was responsible for 10 of the illegal contact flags in 2018, while Anderson's had eight and Boger's had seven. Vinovich's crew did not throw a single one, while Corrente's and Carl Cheffers' threw one apiece.

Remember, the league will mix officiating crews throughout the playoffs, but it is still important to know the tendencies of the head referee of each crew leading into these important postseason games. Be sure to check back each week for more analysis of the playoff referees all month long.