The N.F.L. off-season has gotten shorter since the regular season was extended to 17 games, and it certainly feels shorter, too, given that once-mundane calendar entries, such as the start of off-season workouts, are now treated like red-carpet events.

Yet the down time between last season and this one is still long enough that impactful free-agent signings, un-retirements and rules changes made months ago have receded to the background. Here’s our refresher on the N.F.L. happenings to keep in mind as the regular season begins in earnest on Sunday.

Damar Hamlin is back.

Eight months after Hamlin, a Buffalo Bills safety, went into cardiac arrest during a “Monday Night Football” game, he made the team’s 53-man roster and will backup starters Micah Hyde and Jordan Poyer. Hamlin spent nearly a week in the intensive care unit of a Cincinnati hospital after he collapsed on the field following a collision during a Jan. 2 game against the Bengals. He was then transferred to a hospital in Buffalo.

He steadily passed checkpoints during the off-season, from being cleared to resume football activities in April to playing in his first game since the life-threatening medical event, an exhibition in August. “I made the choice that I wanted to play,” Hamlin, 25, told reporters afterward, adding that he won’t have any hesitation when he’s on the field. Buffalo’s Week 1 game is a return to “Monday Night Football,” against the Jets in East Rutherford, N.J.

Eric Bieniemy left Kansas City for Washington.

After a decade working under Coach Andy Reid in Kansas City, first as the running backs coach and then as the offensive coordinator, Bieniemy is forging out for Washington, where he’s the Commanders’ sole offensive play-caller as well as an assistant head coach. Bieniemy worked with Reid to develop and run the league’s most exciting offense, helmed by Quarterback Patrick Mahomes, as the team won two Super Bowl rings in the past four seasons. But also during that time frame, Bieniemy interviewed for more than a dozen N.F.L. head-coaching jobs without receiving any offers.

In Washington, he has the chance to run an offense away from Reid’s shadow. The transition hasn’t been entirely smooth: Commanders Coach Ron Rivera said last month that some players were “concerned” with Bieniemy’s intense coaching style, before Rivera apologized for putting “my foot in my mouth.” Some intensity is clearly needed, as Bieniemy has been tasked with reviving an offense that has perennially ranked near the bottom of the league.

Tua Tagovailoa didn’t retire.

After Tagovailoa, the Miami Dolphins’ starting quarterback, sustained two diagnosed concussions during the 2022 season, he admitted in an April news conference that he considered retirement before concluding that he was not ready to walk away from football at age 25.

The N.F.L. modified its concussion protocol last season after an investigation into how doctors handled Tagovailoa’s return to the field following a hard hit to the head in a game last September. Four days later, he again hit his head in another game and was taken to the hospital, and Tagovailoa then suffered his second diagnosed concussion on Christmas Day, sidelining him for the rest of the season. Tagovailoa said he took up jiu-jitsu this off-season to learn how to protect his body when he falls, an approach unproven to prevent head injury.

‘Thursday Night Football’ games can be flexed.

In another example of how the pursuit of media money shapes sports leagues, N.F.L. owners approved in May a resolution to bring flex scheduling to “Thursday Night Football” on a limited basis, for now. The rule will allow the league to move no more than two games from Sunday afternoon to Amazon’s Thursday night broadcast. The league can only make those swaps of games scheduled between Weeks 13 and 17 and has to provide at least four weeks’ notice.

The Giants co-owner John Mara spoke out against the change, suggesting that it wasn’t in the best interests of players or fans, but the measure got enough votes from other team owners to pass for a one-season trial.

Brian Flores is calling the Vikings’ defense.

After spending last season as a senior defensive assistant and linebackers coach for Pittsburgh, Flores will call defensive plays for the Minnesota Vikings. A judge ruled in March that Flores’s racial discrimination lawsuit against the N.F.L. and its teams can proceed through the judicial system rather than being moved behind closed doors in private arbitration. Flores, who is Black and of Honduran descent, filed suit in February 2022, accusing the league and its teams of discriminating against him and other coaches of color in its hiring practices.

Players can fair catch kickoffs.

In the latest rule change addressing plays that have been found to be the most dangerous, the N.F.L. this season will allow players to call for fair catches on kickoffs and on free kicks after a safety. If a player makes a fair catch behind their team’s 25-yard line, the ball will then be placed at the 25, mirroring the rule that has been used in college games since 2018.

The league expects the return rate, and thus the number of concussions sustained on returns, to decrease as a result of this change, which will be evaluated and considered for permanent adoption after the season.

Ten players are serving gambling suspensions.

Widespread legalized sports betting in the United States has become increasingly entwined with the N.F.L., even as the league in the past year delivered its most extensive set of penalties for violations of its gambling policy. Ten players are currently serving suspensions, ranging from six-game penalties for betting on other sports while at team facilities to indefinite suspensions for betting on N.F.L. games.

The N.F.L. has asked the public to take its word that no games were compromised, while critics have pointed out the dissonance between the league’s stringent penalties and its growing partnerships with betting companies.

Sean Payton is back.

Given the myriad ways Payton has made his presence known, such as by saying that Nathaniel Hackett’s term with the Denver Broncos, in which he did not make it through a full season, was “one of the worst coaching jobs in the history of the N.F.L.,” it’s unlikely Payton is off anyone’s radar.

But it is easy to forget that just a year ago, he spent Sundays sitting on the Fox Sports set as a commentator, having “retired” after 15 seasons leading the New Orleans Saints.

His run with the Saints, which included one Super Bowl ring, overlapped with that of quarterback Drew Brees. Now, Payton has perhaps the toughest challenge of his career: rehabilitating Russell Wilson. His approach has been hard-charging, starting with his proclamation at his introductory news conference in Denver that, unlike last season, Wilson’s personal performance coaches would not be allowed in the team facility.

Odell Beckham Jr. is part of the Ravens’ new-look offense.

After spending the 2022 season out of the league while recovering from a knee injury he sustained in Super Bowl LVI, Beckham signed with the Ravens in early April. He joined Baltimore just weeks before the team broke a stalemate with quarterback Lamar Jackson, whom it signed to a five-year, $260 million contract extension.

There’s a good deal of anticipation around the league for how the Ravens’ offense will look. Jackson has a new offensive coordinator, Todd Monken, for the first time since his first full season as an N.F.L. starter. Along with Beckham, the Ravens also added Zay Flowers and Nelson Agholor to a receiver group that had been spotty.

Teams can use an emergency third quarterback.

The last labor agreement between the N.F.L. and the players’ union expanded game-day rosters to as many as 48 players, up from 46. A new rule put in place this off-season gives teams additional roster flexibility, allowing them to dress a 49th player as an emergency third quarterback. For the player to enter the game, two other quarterbacks on the game-day roster must be unavailable due to injury or disqualification.

The utility for this role came into focus during the N.F.C. championship, when both the San Francisco 49ers’ quarterbacks were injured during the game, forcing the starter Brock Purdy to return after he had injured his throwing elbow. The 49ers lost, 31-7, to the Philadelphia Eagles.

The Super Bowl will be in Las Vegas for the first time.

When the Raiders moved to Las Vegas from Oakland, Calif., in 2020, the team brought with it the possibility of the N.F.L. world descending on The Strip for marquee events, even if the team’s performance of late has kept it far from the league’s biggest games. After hosting two Pro Bowls, Allegiant Stadium will welcome its first Super Bowl this season, though not without caution for players and personnel around the league: New Orleans Saints running back Alvin Kamara is serving a three-game suspension for his role in a fight in Las Vegas on the eve of the 2022 Pro Bowl. And Super Bowl LVIII is sure to be plastered with betting advertisements and partnerships, while the league continues its crackdown on potential violations of its gambling policy by players.