The NFL will kick off its regular season Thursday night after a busy offseason of rule changes and policy adjustments that will modify what fans see on Sundays, Mondays, Thursdays and -- new for 2023 -- one Friday.

Our annual review of those changes includes the revival of a limited "third quarterback" rule, an expansion of late-season flexible scheduling and the NFL's latest attempt to reduce kickoff returns. We've also noted a few rule proposals that you might have thought the league adopted, or at least hoped it would, but instead left unaddressed for this season.

Much of this work flowed through the league's competition committee, which has undergone changes in recent years and now includes one owner, three team executives, one general manager and four coaches. The full membership:

• Atlanta Falcons CEO Rich McKay (chairman)

• New York Giants owner John Mara

• Cincinnati Bengals executive vice president Katie Blackburn

• Dallas Cowboys COO Stephen Jones

• Miami Dolphins general manager Chris Grier

• Carolina Panthers coach Frank Reich

• Washington Commanders coach Ron Rivera

• Pittsburgh Steelers coach Mike Tomlin

• Tennessee Titans coach Mike Vrabel

Third QB rule returns with a twist

The NFL brought back a rule that allows teams to carry an active third quarterback on game day without having him count against the NFL-imposed roster limit. But there are new stipulations that likely will limit the use of this option.

The third quarterback must be part of a team's 53-man roster. He can't be promoted from the practice squad via a standard elevation for that role. The third quarterback can enter the game only if the top two are injured, and he must be removed if either of them are cleared to play by medical officials. The referee is charged with keeping track of whether the third quarterback is eligible to play.

As a result, only 12 of the league's 32 teams kept three quarterbacks on their initial 53-man rosters last week. Owners approved the rule largely because the San Francisco 49ers ran out of healthy quarterbacks while losing the 2022 NFC Championship Game, and its language makes the rule best viewed as reinforcement for must-win situations.

A lengthy Q&A distributed this week by the league uses the phrase "bona fide" five times to describe eligibility requirements for this rule, a warning to teams who might look for a way to manipulate their game-day rosters. The memo also closes a loophole some teams might have been contemplating: Putting their third quarterback on the 53-man roster but keeping their No. 2 quarterback on the practice squad. Both the No. 1 and the No. 2 quarterback must be part of the 53-man roster in order for the No. 3 quarterback to be eligible to enable utilization of the game-day roster exemption.

Flex options for Monday, Thursday night games

As part of its new broadcast deals, the league granted flex options in Weeks 12-17 for "Monday Night Football" (ESPN/ABC) and Weeks 13-17 for "Thursday Night Football" (Amazon Prime). The flex schedule for "Sunday Night Football" remains in place as well for NBC.

In other words, the NFL can move out of bad late-season matchups, and move in more attractive games, for all of its prime-time packages in 2023. But flexing into a different day, as opposed to simply moving a Sunday afternoon game into Sunday night, will put a bigger logistical burden on fans.

To that end, the NFL will give teams at least 12 days' notice for Monday night flex changes. And after some owners pushed back on the idea of flexing games to Thursday night, the league extended its minimum notice to 28 days. As a result, league officials have emphasized, flexing a Thursday night game is likely to be a rare event. Brian Rolapp, the NFL's chief media and business officer, said in May that Thursday night flexes are "not something we expect to be commonplace."

And in a first, the NFL will host a game on the day after Thanksgiving -- Black Friday (3 p.m. ET) -- to extend its grip on the holiday weekend. The Dolphins will play at the New York Jets in a game streamed on Amazon Prime.

Fair catches on kickoffs inside the 25 are marked at 25

The NFL has tapped what might be its last option for reducing concussions within its current kickoff structure. For 2023 only, owners approved a rule that incentivizes kick returners to call for a fair catch rather than bring back the ball in certain situations.

The rule could render moot the "pop-up" kicks coaches increasingly have employed in an attempt to hand opponents poor field position. In the past two seasons, such kicks have increased by 23% compared to the previous eight-year average. That surge is the primary reason NFL officials believe concussions have returned to unacceptably high levels on the play.

There has been some thought that coaches would replace "pop-up" kicks with squib kicks that can't be fair caught and could still pin opponents inside the 25-yard line. In the 2023 preseason, there were 27 squib kicks, seven more than in the 2022 preseason. But squib kicks aren't as easy as they look, and the average drive start following a squib this preseason was the 28.9-yard line.

Incentivizing fair catches fits into the NFL's primary strategy for lowering concussions on kickoffs: Reducing returns. The league has projected that this rule will further reduce the return rate to 31% in 2023, with a corresponding 15% drop in concussions on the play.

League officials have suggested the fair catch adjustment is a stopgap attempt to address concussions this season while working on a more fundamental change to kickoffs, possibly modeled after the XFL's low-impact alignment.

Use of No. 0 is now permitted

"Zero" is now a jersey option for all positions except offensive and defensive linemen as the league continues an effort to ensure there are enough eligible numbers for all teams.

As of last week, 20 NFL players had taken zero, including Jacksonville Jaguars receiver Calvin Ridley, Baltimore Ravens linebacker Roquan Smith and Jets safety Adrian Amos. All told, according to ESPN Stats & Information, there were nine linebackers, five receivers, three cornerbacks, two safeties and one running back assigned No. 0 when initial 53-man rosters were formed.

Door open for expansion of QB 'push' sneaks

The competition committee extensively reviewed a play the Philadelphia Eagles utilized often on their run to Super Bowl LVII last season. The strategy calls for one or more teammates in the backfield to push the quarterback past the line to gain, or into the end zone, on planned sneaks. It was perfectly legal under NFL rules, which prohibit pulling teammates but not pushing them, but it reminded critics of rugby.

.@JalenHurts with the QB sneak!@Eagles on the board first! #FlyEaglesFly

: #SBLVII on FOX
: Stream on NFL+ https://t.co/d8gBDzRt2m pic.twitter.com/jfgnU4xfS8

NFL (@NFL) February 12, 2023

But there was no consensus on whether to curb or outlaw the approach, which the Eagles used to supplement quarterback Jalen Hurts' already-strong rushing skills, and there is a pretty strong expectation that it will proliferate in 2023. The league's internal data review revealed 90 such plays across the league last season, with an 84% success rate.

Tripping is a personal foul

An elevation in subtle tripping techniques, and some difficulty in identifying them via real-time officiating, led the NFL to reclassify it as a personal foul and thus shift the on-field penalty from 10 to 15 yards. Making it a point of clarification means officials have been asked to look closely for such infractions, and it's also a warning that players will be subject to fines and potential suspensions even if no flag is thrown during the game.

There were a total of 12 flags thrown last season for tripping, a bit higher than the average of 9.2 per season from 2010 to 2021, and it's fair to expect an uptick in 2023.

Use of helmet rule altered

Established in 2018 to reduce the type of contact that frequently causes concussions, this rule has proved nearly impossible to officiate. As a result, the league has relied largely on warning letters and fines issued after the game to enforce the rule, which originally prohibited a player from lowering his helmet to initiate contact with an opponent. And in the rare instances where it is penalized in a game, the NFL has instructed officials to refer to the infraction generically as "unnecessary roughness."

Over the ensuing five years, the league has issued an average of 191.4 warning letters and fines per season. In a sign of the difficulty in changing this particular behavior, it set a record of 229 in 2022. But even postgame discipline has proved problematic, as players have successfully appealed roughly one-third of the fines by arguing the helmet contact was incidental rather than an overt attempt to initiate. So in 2023, the league has tweaked the rule to make successful appeals less likely, removing the requirement to "initiate" contact and adding specific examples of impermissible contact.

The fines are significant: $21,855 for a first offense and $43,709 for a second, as Pittsburgh Steelers linebacker Kwon Alexander found out during the preseason.

Automatic review for failed fourth downs

Instead of jumping ahead on proposals to make all plays eligible for replay review, or employing a sky judge, the NFL has embraced a slow addition of applicable circumstances. Failed fourth downs are the latest supplement to the list of automatic reviews that don't require a coach's challenge.

The league takes comfort in this approach because it has managed to decrease official reviews by 28% over the past two seasons, and in turn drop its average time of game. The decline in reviews is due largely to the "replay assist" program, established in 2021, that allows replay officials to jump in quickly to correct or confirm rulings without going to a formal review.

And when it does go to an official review, the league has managed to make it shorter through use of Hawk-Eye technology that displays all camera angles instantly. Overall, the average time of game in 2022 was 3 hours, 1 minute and 40 seconds, the NFL's lowest since 1993.

No review for roughing the passer

NFL teams set a non-strike-season record in 2022 by using 68 different starting quarterbacks, according to ESPN Stats & Information, amid season-long concern for the health of Miami Dolphins passer Tua Tagovailoa. A subsequent series of questionable flags for roughing the passer renewed calls for making the penalty reviewable in replay, but owners never came close to making such a dramatic rule change.

Ultimately, roughing the passer penalties dropped 38.6% in 2022 from 2021, largely because of a point of clarification to avoid flags for incidental contact. But that didn't apply to what is currently the most controversial aspect of roughing the passer, a prohibition against what the NFL rule book describes as "unnecessarily or violently" throwing down the quarterback or landing "on top of him with all or most of the defender's weight."

One referee who was involved in several debatable "body weight" calls, Jerome Boger, retired in the offseason. Otherwise, the only new guidance the NFL has given teams is to coach defenders to avoid approaching a quarterback "down the middle." Instead, they should approach from the side to minimize the chances of landing on the quarterback and getting penalized.