Nielsen television ratings have joined QBR and yards-after-catch in the lingo of NFL fandom. (Jeffrey T. Barnes/AP)

The NFL’s Thursday night season opener last week — a Philadelphia Eagles victory over the Atlanta Falcons — averaged 19 million viewers on NBC. That number was down from the year before, so on Sunday morning, President Trump weighed in.

“Viewership declined 13%, the lowest in over a decade,” Trump tweeted gleefully, the latest salvo in his on-and-off squabble with the league. Widespread coverage of the tweet followed across political and sports media, the latest reminder ahead of the league’s opening weekend that its ratings had tumbled 10 percent last year and 8 percent the year before.

Then on Sunday, the NFL got good news. CBS reported that its ratings jumped nearly 30 percent from a year ago and that it had its most-watched opening weekend singleheader since 1998. (CBS didn’t have a national afternoon game.)

Bloomberg called the numbers a “ray of hope” for the league. There was no Trump NFL tweet Monday.

The NFL’s much-covered ratings slide has coincided with player protests, serious questions about player safety, sometimes controversial rule changes and a changing media landscape. It has created a sense of uncertainty about the future of the league, even as football remains a commanding cultural institution. As Mark Leibovich posits in his new book, “Big Game: The NFL in Dangerous Times,” the league feels “perched between world domination and sudden death.”

Add in Trump’s attacks on the players, who have protested against racial inequality during the national anthem, and the league’s trajectory has come to represent something bigger than just football. The NFL’s weekly ratings can feel like a referendum on the future of TV, on America’s most popular sport and on Trump, a man with a certain fondness for ratings.

“It’s like the unemployment numbers that come out once a month,” said Ari Fleischer, a White House press secretary under President George W. Bush. “Rightly or wrongly, it’s a weekly news hook where one side gets to ratify its view.”

On Friday, NBC put out a news release that found a silver lining from the Eagles-Falcons matchup: Its 19 million viewers more than doubled the combined prime-time audience of other broadcast networks. The 13 percent dip also could be considered an unfair slant: The game was delayed nearly an hour by weather.

By the end of the weekend, Fox’s numbers were slightly up, while ratings for the Sunday and Monday night games were down. In sum, the NFL’s weekend ratings were relatively flat vs. last year.

But does it mean anything?

The variables — the matchups, the weather, the news of the day and the competitiveness of the games — make week-to-week comparisons difficult. CBS’s 30 percent bump, for example, comes in comparison with a week last year when Hurricane Irma devastated parts of Florida.

“You really can’t tell anything from one week,” said Marc Ganis, a consultant for several NFL teams, though he added that the larger trends become important as the sample size grows.

The macro view, the networks like to say, is that regardless of ratings points, the NFL, relative to everything else on TV, is in better shape than ever. And they’re right. The five highest-rated shows last week were NFL games.

“The NFL is still the biggest thing out there,” said Neal Pilson, who ran CBS Sports from 1976 to 1995. “If you want to sell cars, you still have to go to the NFL.”

But that doesn’t make the overnight numbers any less irresistible.

“I go on Twitter now, and I can’t believe how many people care about this stuff,” said Patrick Crakes, a former executive at Fox Sports who moved into media consulting two years ago. It’s also not just the NFL. When Tiger Woods makes a run on a Sunday afternoon at a golf tournament, fans tweet GIFs about executives licking their lips and counting their money.

“There’s a greater interest in media,” Crakes said. “It’s a greater part of people’s lives now, and it’s changing.”

While the politicization of the NFL’s ratings may be new, television executives said the ratings themselves — and football on TV, writ large — have long been a cultural touchstone. When Fox outbid CBS for the rights to NFL games in 1993, “Saturday Night Live” aired a skit in which Chris Farley played jovial announcer John Madden. The joke was that Fox, known for its sophomoric TV lineup, was going to cover football with a “Married With Children” sensibility.

The interest in weekly numbers isn’t entirely new, either.

“Reporters would call me up 30 years ago on a Monday morning and say, ‘You’re down 8 percent,’ ” Pilson said. “I’d say, ‘So what?’ ”

More recently, at least pre-Trump, fascination with the NFL’s ratings has centered on the league’s exceptionalism. As the cable bundle has frayed over the past decade and a fractured media landscape has carved up audiences, the NFL’s ratings held steady and often went up before 2015.

“The story was, look, the NFL isn’t going down and everything else is going backward,” Crakes said. “It was amazing!”

But the past two seasons have shown that even the NFL isn’t immune to changing media realities or the contentious politics of the Trump era.

If there is one tangible benefit that can be drawn from Sunday’s positive numbers, said Frank Hawkins, the former head of business affairs and media affairs for the NFL, it’s that it headed off a Trump tweet this week. There was probably no celebration or panic after this past weekend’s returns in the league office, Hawkins said, but the less Trump talks about the league, the better it will be able to analyze its own data.

“So maybe now Trump tweets less,” Hawkins said. “That helps separate the signal from the noise.”