DOVER, Del. — They say races aren’t won or lost at the start.

Restarts are another story, especially given NASCAR’s increased scrutiny of them in recent weeks. Restarts could be the key factor Sunday in the AAA 400 at Dover International Speedway when the 16 drivers competing in this year’s Chase for the Sprint Cup get whittled down to 12.

After three consecutive races in which controversial restarts and penalties (or lack thereof) were major talking points, NASCAR took action by increasing video monitoring and putting human observers in place at the restart zone last week at New Hampshire Motor Speedway. Those moves contributed to Team Penske’s Brad Keselowski becoming the first driver to be penalized for jumping a restart since the crackdown began.

This week, NASCAR has doubled the length of the restart zone at Dover from 70 to 140 feet. That number varies by track and has always been calculated based on the length of the track and the pace car speed, but after listening to feedback from the drivers, NASCAR chose to give the drivers more space to work with, something it believes will ultimately benefit the race leader.

“To lengthen that box, I think, is a great move,” six-time Cup Series champion Jimmie Johnson said. “I’m hopeful that they lengthen the box and bring it closer to the start/finish line. I think it will slow down some of the three and four wide into Turn 1 scenarios we have had. It will be less distance to get speed built up closer to the start/finish line, and I think we will maybe control that space a little bit better.

“We should have really better side-by-side restarts, which is what everybody is after,” he added. “Obviously, the goal here is to give control back to the guy that has earned it — to the leader. That’s what happens and I am in favor of it. It’s a good call and I am excited to see how it plays out.”

Keselowski said NASCAR made an example of him after it deemed him guilty of taking over a restart from leader Greg Biffle last week at New Hampshire even though Keselowski didn’t actually ever take the lead as a result. The 2012 Cup champion dropped to the tail of the lead lap but recovered to finish 12th.

Keselowski was unhappy with the penalty. But in the aftermath, many drivers were pleased NASCAR finally drew a line in the sand and called a violation even if the offense looked less blatant than restarts that drew attention in the previous two races at Richmond International Raceway and Chicagoland Speedway.

“There’s gonna be plenty of gamesmanship still, and I think NASCAR has also set the precedent with what they did last week and enforcing the rule,” Keselowski’s teammate Joey Logano said. “That’s something they need to continue doing. It’s not just having it happen one time and then scare us, and then don’t do anything about it for the next three weeks.

“They finally put their foot down last week on what we can and can’t do, and that rule needs to be consistent to make sure that when they see something they make the same call and be consistent with that.”

From NASCAR’s perspective, the key is that the race leader must make the first move in terms of restarting the race. That doesn’t guarantee he is going to lead the race at the start/finish line — or even at the end of the restart zone for that matter. NASCAR just wants everyone to have the impression that the leader is the driver who controls the restart, even if he ultimately loses the lead on that restart.

“We listened to the drivers, we listened to the competitors, and we analyzed the situation,” said Sprint Cup Series managing director Richard Buck, speaking to Sirius XM NASCAR’s “Dialed In” program. “The rules have not changed. The leader has earned the right to restart the race and the whole idea was to reward the leader — for having the best pit stop, being the fastest guy, etcetera — and give them the opportunity to restart the race in that zone.

“We opened that zone up because the leaders felt they were a bit of a sitting target.”

Hendrick Motorsports driver Jeff Gordon, who has famously struggled with restarts, said as part of his team’s analysis, engineers determined that drivers have barely a second to work with in the restart zone. Following drivers were often able to hang back and get a run on the leader if they timed their acceleration just right.

The longer restart zone, which gives the leader additional time to decide where and when to accelerate and trigger the restart, should restore more control to the leader.

“I absolutely love it,” Gordon said. “I think it’s a great move and I’ve been asking for this for a while.

“People pushed the limits on that and forced NASCAR to make this box that we currently have,” he continued. “The [restart] box was always too small. It just makes the whole front row very vulnerable, and not just the second-place car, but the leader as well. It needed to be bigger; my only question is did they go big enough?”

It’s bound to make the restarts at Dover on Sunday interesting, especially with the race serving as an elimination round for the Chase. At the eye of the storm is defending Cup Series champion Kevin Harvick, who has been forced into a must-win situation after a disastrous 42nd place finish at Chicagoland and the disappointment of running out of fuel at New Hampshire with fewer than three laps remaining after dominating that race.

There’s drama at the cut line with fan favorite Dale Earnhardt Jr. holding the 12th and final transfer spot heading into Dover. But Earnhardt is just one point ahead of Busch, the hottest driver in the second half of the season, with four wins since he returned in May from injuries he suffered back in February at Daytona.

With the grid set by points after qualifying was rained out, and fewer than 45 minutes of quality practice time available on Saturday, Sunday’s 400-lapper at the Monster Mile could be a wild affair.

“I don’t know what to expect,” said Keselowski, who is eighth in the standings with a 16-point cushion over the cut line at 13th place.

“That’s part of the fun.”