Last season, at the first NASCAR Monster Energy race, Martin Truex Jr. went to the lead, caught some clean air, and then rocketed away from the field for a comfortable victory.

It was the type of race that NASCAR officials believed was keeping the sport from being appealing to fans.

NASCAR wanted closer finishes and races with lots more passing and side-by-side racing.

So it changed some rules for the 2019 season.

The base package for cars would feature a taller rear spoiler, a larger front splitter with two-inch overhang, and a wider radiator pan. On tracks more than a mile in distance, tapered spacers would be used to reduce horsepower, and on most intermediate tracks, front aero ducts would be incorporated.

All that was done to put more cars in situations that made races closer.

What that base package also has changed is the anticipation for how a race will play out on tracks that drivers were once familiar with. Each race thus far has been a learning experience in how things might play out.

“The Tricky Triangle” at Pocono Raceway, which will host the Pocono 400 on Sunday, has long been one of the more challenging tracks, and now drivers might consider themselves novices until they figure out how the new base package will affect the racing.

“I don’t even know what to expect,” said Alex Bowman, who placed third at the second Pocono race last season. “It’s going to be really interesting to try to adapt to it there.

“You’re not going to be able to drive wide-open. You’ll be lifting, but the cars create so much drag that you want to be able to really use any brake. It’ll really be just off-throttle times in the corners.

“We won’t be shifting, which will be different for us at Pocono. We’ll just have to wait and see because it’s going to be vastly different.”

The first-half statistics show that the new package is having the desired effect.

Through the first 13 races, there have been 513 green-flag passes for the lead compared with 330 at this point last season (an increase of 55.5 percent). Three of the races have produced record-setting green-flag passes for the lead: Las Vegas; Bristol, Tenn.; and Kansas. Nine of the races have had an increase in green-flag passes throughout the field.

“We are halfway through our regular season. We’ve had a chance now to see the package on just about every type of track that we race on with the exception of road courses, and that’s coming up soon,” John Probst, NASCAR’s senior vice president for innovation and racing development, told Motorsport.com on Wednesday.

“All of the key stats that we track are up, and some of them are up pretty substantially.”

For the drivers, it’s just another adjustment to make.

“I’m looking forward to it because I like new things,” said Bowman, who has three second-place finishes in the last four races. “Being able to go [to Pocono] and try to adapt quicker than everyone else will be a lot of fun.

“We’re all in the same boat. We’re all racing on the same track with the same package. Growing up in this business, I got to a lot of places you have not seen before, drive cars that I hadn’t before.

“This kind of goes back to that. … It should definitely be interesting. I find it exciting.”