Whether he’s recruiting in the Pacific Northwest, Texas or any cranny in between, Washington coach Chris Petersen always asks high school coaches about numbers.

Not uniform numbers. Not heights and weights. Not 40 times and reps on the bench.

Petersen wants to know about player participation.

“How are your numbers?”

The responses from coaches in one state — for the Pac-12, the most important state — are not encouraging.

High school football participation in California is declining, rapidly.

“We’ve noticed,’’ Petersen said. “I think it was huge early on with the concerns about concussions. You go to suburbia, and the soccer moms are like, ‘My son’s not playing that sport.’

“That said, I was just in southern Washington, and things seemed to have calmed down a little. People are getting better educated.

“But the California thing? Oh, yeah, there’s no question.”

The Pac-12 is facing numerous challenges as it attempts to keep pace with the SEC, Big Ten and other Power Five conferences, from the eat-your-own nature of its schedule to the lack of TV exposure to revenue for operations.

But there might be no greater threat over the next five or 10 years than a shrinking talent pool in its primary pipeline.

According to data collected by the National Federation of State High School Associations, participation in 11-on-11 tackle football in California has dropped 8.8 percent in the past five years:

2013 season: 103,474

2014 season: 103,740

2015 season: 100,205

2016 season: 97,079

2017 season: 94,286

Numbers from the fall of ’18 won’t be available until this summer, but Roger Blake, executive director of the California Interscholastic Federation (CIF), expects the decline to continue.

The primary reason, he said, is parental concern about injuries — in particular, head trauma.

“You used to see high school teams with 60, 70, 80 kids on the sideline on Friday night,’’ Blake said. “Now, it’s 30 or 40. Moms and dads think there’s a risk being out there, so they say, ‘Go play something else.’’’

There is a morsel of good news for the Pac-12: The other five states in the conference footprint haven’t experienced the same decline.

Participation in Washington, Oregon, Arizona, Utah and Colorado has dropped a combined 2.8 percent (in raw numbers: about 2,000 players) over the same timeframe.

Then again, California has approximately 20,000 more high school football participants than the other five states combined.

“We’ll see over the long term if it continues the downward trend,’’ Oregon State coach Jonathan Smith said. “That wouldn’t be good. California is the lifeblood of the Pac-12.”

Relative to other Power Five conference, the news is even worse for the Pac-12:

The primary pipelines for the SEC, ACC, Big 12 and Big Ten have not experienced nearly the same level of participation decline as California.

In fact, numbers are up slightly over the past five years in Texas (164,544 to 164,664), Florida (40,606 to 41,852) and Georgia (32,979 to 33,027) while declining about four percent in Ohio (44,431 to 42,637).

“It’s so laid back on the West Coast — football’s just not as important to them,’’ said Mike Farrell, the national recruiting director for Rivals. “If there’s an opportunity to get injured, some parents just pull the kids out.

“But in Texas, it’s part of the culture. In the southeast, there’s a swagger about playing football. In the northeast and midwest, there’s just a toughness about the mentality.

“I could see kids losing interest in California. You can play so many different sports.”

Concern over concussions might be the primary force driving kids out of football, but it’s not working alone, according to more than a half dozen college coaches, recruiting analysts and high school administrators interviewed for this article.

A lack of resources plowed into the football programs (relative to states like Texas and Florida) and the number of options were also cited.

“We play soccer in the winter,” Blake said. “How many other states do that?”

Indeed, participation in soccer in California high schools has jumped by 10 percent over that past five years.

Track numbers are up.

Water polo numbers are up.

Lacrosse numbers are up.

Even volleyball participation has, um, spiked.

“It’s a culture thing,” said Smith, who grew up in Southern California. “Get into nature, play lacrosse, go snowboarding. I don’t know if it’s a downward spiral yet (in football), but there’s definitely a lull.”

What’s more, the increase in football transfers has created an anti-competitive environment, with elite players clustering in certain leagues and teams, leaving other programs to wilt.

In Southern California, the Trinity League, which includes Mater Dei, St. John Bosco and Serra, is the ultimate destination for players hoping to earn college scholarships.

“The parity is out of whack,” Petersen said, “and if your team isn’t as good, maybe it’s easier to stop playing.”

Utah coach Kyle Whittingham believes the number of elite players available to recruit each year remains unchanged, and anecdotal evidence suggests he’s right:

The number of California players ranked in the top 250 of the 247sports composite — the 5- and 4-star prospects — is essentially unchanged over the past five years.

“There’s no doubt, we see (a decline), starting at the Little League level,’’ Whittingham said. “But the ones that are opting out are the marginal players.’’

But marginal players matter to the system; some of them become late-bloomers that are heavily recruited — and it could be just a few years before Pac-12 schools feel the full impact of a shrinking pipeline.

Participation in youth football is in a well-documented decline, and Blake expects the CIF losses to continue for at least several seasons. His hope is that improvements in concussion education and prevention eventually take hold, thereby halting the exodus.

Even in that best-case scenario, California would have lost 20,000 high school players over an eight- or nine-year span, and other states in the conference simply don’t have the participation numbers to offset the losses.

That could force Pac-12 programs with mostly regional appeal to recruit more heavily outside the footprint, where participation remains steady and competition for elite prospects is fierce.

“USC is the Pac-12’s only true national recruiter,” said Tom Luginbill, an ESPN analyst and its national recruiting director.

“It’s the one program with a national brand, that can go into the home of a top prospect from another region and everybody will recognize the emblem is that of a blue-blood.”

Perhaps the most ominous sign of all came in the summer of 2017, when Long Beach Poly, one of the most successful programs in high school history (Mark Carrier, DeSean Jackson, JuJu Smith-Schuster), dropped its junior varsity program because of low numbers.

Petersen isn’t worried about a dearth of star players — at least not yet. His concern at the moment is the dwindling depth and the ripple effect that could have.

“More than anything, football is a numbers game,’’ he said.

“You have to have numbers in case guys get hurt. You have to have numbers to practice. Numbers to help guys get better. It’s really, really important.

“All those guys on the fence about playing, you need the bodies in the building.”

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