Updated

NASCAR is about to start finding out whether its offseason changes will pay off on tracks like Las Vegas Motor Speedway.

NASCAR worked tirelessly behind the scenes last year to improve its on-track product, particularly at 1.5-mile speedways that had turned into glorified parades. After the drivers opened the season on Daytona's superspeedway followed by Phoenix's quirky mile oval, it's time for the first of 11 races on 1.5-mile tracks.

While fans watch defending champion Matt Kenseth and early points leader Dale Earnhardt Jr., everybody on the north end of The Strip is eager to see if passing is any easier and if the racing is any better Sunday in Vegas.

Gene Stefanyshyn, NASCAR's vice president of innovation and racing development, warned that one show won't be a true barometer of the changes made to the rules package.

"We can't jump too quickly and say that this is the answer," Stefanyshyn said. "Some teams will take some time to figure it out. I think the aero piece of it, it's pretty much set. It's just a matter of getting the driver to find the limit and feeling comfortable with the aero.

"But the chassis, the engineers will play around with it for a while until that settles down. Then the driver will begin to find the sweet spot and get comfortable. We won't have a good feeling where all this lands until we get about three under our belt, and that would be the Texas race."

NASCAR's new package also will be scrutinized March 23 at Fontana and April 6 at Texas.

Those three races last year had a combined 57 lead changes. In comparison, this year's Daytona 500 had 42 lead changes.

NASCAR won't get Daytona-like passing at speedways, at least not anytime soon. And Stefanyshyn wants to give this rules package some time before tinkering again.

"There's a learning curve here," he said. "I think you can't be too premature on this. There's a lot of cars. There's a lot of different engineers, a lot of different thoughts on getting down the learning curve. So we'll wait and see and see how it all plays out."

Here are five things to watch in NASCAR's third race of the season:

JUNIOR'S JUMP: Dale Earnhardt Jr. has never won at Las Vegas, and he frequently struggled in Sin City early in his career. But his outstanding start to the season suggests he might be accomplishing a whole lot of firsts this year. The Daytona 500 champion had top-three finishes at the final two 1.5-mile tracks of last season, and his Vegas confidence is strong after a testing session. Vegas bookmakers always depress Earnhardt's odds because of his popularity, but he's truly among the favorites for a big finish.

KENSETH'S LABOR: Defending champion Matt Kenseth is clearly comfortable in Las Vegas after three wins on this track, but he's still wondering how NASCAR's changes will translate in competition on 1.5-mile ovals. "It's really hard to compare anything from the past," he said. Kenseth also believes the Vegas track has aged, becoming slower and slicker. He expects the drivers to run wide, which could make for exciting, unpredictable racing.

PENSKE POLES: The Penske Ford teams seem to be figuring out NASCAR's changes quickly. Joey Logano and Brad Keselowski have qualified in the top two spots for two straight races, with Logano sitting on the pole Sunday in Vegas after obliterating the track speed record. "To have a Penske front row the last two weekends at two completely different racetracks just goes to show how hard these guys have been working," Logano said. "When you work hard, results come. Obviously we haven't won on Sunday yet, so we've got to figure out the big show, but we've had good speed in our cars."

HOMETOWN HEROES?: Kurt and Kyle Busch grew up in Las Vegas, but the brothers don't get treated like returning heroes — at least according to Kyle, the 2009 Vegas champion. Kyle's theory is that the Busch boys won so many local races growing up that they alienated a big chunk of the local racing fan base. Both drivers are still eager for their first victories of the season, and Kurt is grateful to focus on racing again after so much attention this week around his upcoming attempt to run the Indianapolis 500 and the Coca-Cola 600 on the same day.

BIG TICKET: Judging by the larger-than-normal crowds at Friday's qualifying session and Saturday's compelling Nationwide Series race, NASCAR is still a hot ticket in Vegas. The speedway also got the benefit of a huge construction trade show in town this weekend, allowing plenty of racing fans to get their fix on a long weekend.

___

AP Auto Racing Writer Jenna Fryer contributed to this report.