NASCAR's popularity is seemingly on the wane, but Dale Earnhardt Jr. says it can grow again, perhaps even back to its peak during his prime driving days.

One caveat, though: It will "take a long time.

"The growth of our sport to its peak, that took decades," Earnhardt said. "That took more than 10 years, 20 years, that was a 50-years process," he said in a phone conversation with the Detroit Free Press Friday, ahead of Sunday's Monster Energy NASCAR Cup Series race at Michigan International Speedway. "You can take that apart overnight. It can be broken easily. Building it up again is going to take that same perseverance."

NASCAR's attendance woes were apparent in early April, when Bristol Motor Speedway, hosting the Food City 500, appeared to be more than half empty. NASCAR does not release attendance figures, but the Associated Press reported the following:

"The Coliseum-style structure now holds 146,000, but the crowd size has shrunk so much over the years that Bristol last weekend did not even sell tickets in the turns.Closed sections included the Darrell Waltrip Grandstand on the same weekend the Hall of Famer and all-time winningest driver at Bristol was feted for his upcoming retirement from broadcasting."

Reported estimates for the race's attendance were about 35,000-40,000, according to Forbes' Dave Caldwell, with even the open sections only sparsely populated. Other tracks have completely removed some grandstands.

But Earnhardt sees the potential for growth.

"I know that the tracks and the industry want things to get better, they want more fans to be at the racetrack," Earnhardt said. "That's just going to take a long time. It's not going to happen overnight, not going to be next year, not going to be five years from now."

Earnhardt is optimistic about Michigan's prime driver, Rochester Hills native Brad Keselowski. Keselowski, ranked No. 6 in the Cup standings, has never won in 20 Cup Series races at Michigan International Speedway. Earnhardt can sympathize; he grew up in North Carolina, but never won in 35 Cup Series races at his "home track" in Charlotte.

Earnhardt said he thinks Keselowski has a good chance to snap that streak on Sunday in the Consumers Energy 400. Earnhardt said Keselowski was "head and shoulders above the rest" at a practice round Friday morning. Keselowski claimed the pole in qualifying on Friday afternoon, with a speed that was nearly half a mile-per-hour faster than any other driver. Still, he'll need a bit of luck to break through.

"I don't think that its track really challenges any driver," Earnhardt said. "It really comes down to showing up and being the best car and having everything work out for you here."

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Keselowski's Penske teammate Joey Logano won at MIS in June, and Earnhardt is confident Keselowski can do the same Sunday.

If it does happen, Earnhardt will be there — just not at track level.

These days, the 44-year-old is a full-time member of the media with NBC Sports. He mostly covers NASCAR, but also worked the 2018 Winter Olympics in South Korea, last year's Super Bowl and this year's Kentucky Derby.

"It was trial by fire in a way because of my inexperience," Earnhardt said. "It was very intimidating and very very scary to jump in there and do some of those bigger events like that, but I was a fish out of water and just embraced that aspect of it."

Earnhardt has also appeared in various music videos featuring Kid Rock, Jay-Z and Sheryl Crow. He's even penned a book.

Take a look at Earnhardt and fellow motorsports legend Danica Patrick in Jay-Z's "Show Me What You Got," which was released 10 years ago.

Of course, his job with NBC means he still keeps a close eye on the sport that made him a star. So who's the next big NASCAR star?

"There's really no stone left unturned in terms of who might sneak up in there and surprise everybody," Earnhardt said. "It's pretty much straightforward who the bright stars are."

Contact Greg Levinsky: glevinsky@freepress.com. Follow him on Twitter @GregLevinsky.