The NFL's new kickoff rule is here to stay with a slight tweak. What else is changing?

(The Associated Press) -- The NFL's one-year experiment with the new kickoff rule becomes permanent this season with a new tweak that the league hopes will lead to a bigger increase in the rate of returns.

The league also approved changes to the overtime rule, expanded replay assist and made a few other technical changes for this season. Those were on display during the exhibition opener Thursday night between the Detroit Lions and Los Angeles Chargers that also featured the NFL's Hawk-Eye virtual measuring that replaced the old-time chains to determine first downs.

The league experimented with the so-called dynamic kickoff in 2024 in hopes of more returns while also making the play safer. Owners voted in April to make the change permanent while moving touchbacks on kicks that reach the end zone on the fly from the 30 to the 35, which is expected to lead to more kicks in play and more returns.

There was no change in the tush push play that Philadelphia used so successfully on the way to winning the Super Bowl last season.

Here’s an explanation of some of the new rules that will be in place.

What’s new with the kickoff?

The league was mostly pleased with the experimental kickoff put in place for 2024 that led to the rate of kickoff returns increasing from a record-low 21.8% in 2023 to 32.8% last season, while reducing the rate of injuries on what had been the game’s most dangerous play.

The rule made kickoffs more like scrimmage plays by placing the coverage players and blockers close together to eliminate the high-speed collisions that had contributed to so many injuries on the play. The league said the rate of concussions dropped 43% on returns, with a significant reduction as well in lower-body injuries.

The problem last season was many teams still opted to kick the ball in the end zone because the touchback wasn’t punitive enough. The average starting field position on a touchback was only 2.4 yards further than the average starting position after returns, which was the 27.6-yard line.

By moving the touchback to the 35, the league projects that the return rate will rise to somewhere between 60% and 70%, with a similar increase in long returns, adding more excitement to the game.

The league also approved a small tweak to how blockers on the return team are allowed to line up in the setup zone that could lead to longer returns.

In the game Thursday night, there were seven returns on the nine kickoffs — including a lost fumble by Detroit on the opening kick. There was one kick that went for a touchback and another that didn't reach the landing zone in the air and was spotted at the 40.

How about onside kicks?

Teams will still need to declare their intention to try an onside kick because of the different formation. But a new change will allow trailing teams to try one before the start of the fourth quarter after Kansas City had to kick deep while down 28 points in the final minute of the third quarter in the Super Bowl.

Coverage players will also be allowed to line up one yard closer in hopes of increasing the rate of recovery from about 6% over the past three seasons to at least 10%.

How will overtime change?

The league approved a proposal to make the regular season overtime more like the postseason, with both teams getting a chance at a possession, even if the team that gets the ball first scores a touchdown.

The NFL added regular season overtime in 1974, adding a 15-minute sudden death period that ended on any score. In 2010, the rule was tweaked to a modified sudden death that required an opening possession touchdown to immediately end the game instead of only a field goal. That was in effect in both the regular season and the playoffs.

Overtime then was shortened for the regular season to only 10 minutes in 2017. A rule change in 2022 for the playoffs only gave both teams the chance to score even with a touchdown on the opening possession.

Now that will be the case in the regular season, after the improved field position on kickoffs made winning in OT on an opening possession TD easier.

According to Sportradar, six of the 16 overtime games last season ended on an opening-drive TD for the most overtime games ended on the first drive since the rule change went into effect in 2010.

In all, teams that won the overtime toss won 75% of the time last season, according to Sportradar, and have a .606 winning percentage in overtime since it was cut to 10 minutes.

The league kept the 10-minute overtime period instead of expanding it back to 15 minutes like was originally proposed by Philadelphia, which could lead to teams opting to go for 2 and a win if they match an opening-drive TD with one of their own since there might not be time for another possession.

Replay assist

The NFL expanded its replay assist system to overturn objective calls if there was “clear and obvious” evidence that a foul didn’t occur. The calls could include facemask penalties, whether there was forcible contact to the head or neck area, horse-collar tackles and tripping. Replay also would be able to overturn a roughing-the-kicker or running-into-the-kicker penalty if video showed the defender made contact with the ball.

The league has been using replay assist in recent years to overturn obvious errors on aspects like whether a pass is caught or where the ball should be spotted without the referee needing to stop the game for a review.

The Competition Committee says there’s no interest in allowing replay assists to call penalties on plays missed by officials on the field.

Other changes

Referees will no longer use the chains to determine first downs, opting instead for a virtual measuring system. This won't eliminate the officials who manually spot the ball and use chains to mark the line to gain.

That was on display Thursday night for the first time after a 10-yard run by Detroit's Craig Reynolds in the second quarter. The officials stopped the game for a measurement and instead of the chains coming on the field, everyone looked at the video board and saw that Reynolds got the first down.

There were some procedural rules changed in regards to injured reserve. Teams can place two players on injured reserve with the designation to return when rosters are reduced to 53 players instead of after. Playoff teams also will be granted two additional return from IR designations.