One open question regarding President Donald Trump's war of words with the NFL: Will it help the TV ratings?

Certainly, pro football could use a lift. NBC said ratings for its Sunday night game between the Oakland Raiders and Washington Redskins was down compared to a week three match-up last season in the same time slot. The network said 11.6 percent of U.S. households saw the game, compared with nearly 13 percent who tuned in to watch the Chicago Bears and Dallas Cowboys square off a year ago.

It's not clear if Mr. Trump's criticism of players who refuse to stand during the traditional pre-game playing of the national anthem is affecting the NFL's viewership, even as he suggested in a tweet this weekend that the controversy is hurting the sport's ratings. For example, CBS Sports said its Sunday NFL coverage for week three was up 4 percent over last year (CBS owns CBS Sports and CBSNews.com.)

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By the same token, it's also evident that America's most popular professional sport is no longer the sure programming bet it used to be. According to Pivotal Research analyst Brian Wieser, viewership for the NFL was down 14 percent on a year-over-year basis during the first week of the 2017-18 season. That's the lowest level of same-week viewing since 2009.

Great solidarity for our National Anthem and for our Country. Standing with locked arms is good, kneeling is not acceptable. Bad ratings! — Donald J. Trump (@realDonaldTrump) September 24, 2017

Many people booed the players who kneeled yesterday (which was a small percentage of total). These are fans who demand respect for our Flag! — Donald J. Trump (@realDonaldTrump) September 25, 2017

As a result, Walt Disney (DIS), parent of ESPN; CBS (CBS), parent of CBS MoneyWatch; Fox (FOXA), parent 21st Century Fox and Comcast (CMCSA), whose properties include NBC, are in a bind. They've counted on the NFL to buttress their business as audiences for cable and broadcast networks have dwindled in recent years. It has been an expensive strategy.

Fox, CBS and Comcast signed a $27 billion deal with the NFL for the right to broadcast games through 2022. ESPN reportedly pays $1.9 billion per year for the rights to "Monday Night Football," a 73 percent increase over the previous contract. NBC and CBS signed a $900 million deal in 2016 for the rights to broadcast Thursday night games.

"The bigger question is why and how have sports defied gravity for so long," Pivotal's Weiser said, adding that broadcasting the NFL had "high fixed costs." He noted: "At the end of the day, people are using their TV sets less than they used to."

Theories abound attempting to explain the ratings drop. Among them: the public's attention being diverted by Hurricanes Harvey and Irma. Before that, the nastiest presidential campaign in recent memory fixated viewers away from the gridiron.

Others have pointed to the controversy around former San Francisco 49er quarterback Colin Kaepernick as a fan turn-off. Injuries to stars such as wide receiver Odell Beckham Jr. of the New York Giants haven't helped, either, nor do the retirements of fan favorites such as Peyton Manning.

Some sports fans have argued that the quality of the league's product has slipped. Some evidence justifies these concerns. According to 538.com, only three games in the season's Week One were decided by 7 or fewer points, the lowest number for an opening week since 1973. Teams combined for 40.4 points per game, the sixth-lowest mark since 2012. Many of the games weren't even close, with the average margin of victory at 3-to-1.

To be sure, the viewership picture isn't entirely bleak. The opening contest on NBC's "Sunday Night Football" featured two of the league's most popular teams, the Dallas Cowboys and the New York Giants. It posted a 5 percent viewership gain over the previous year.

CBS chief executive Les Moonves, for one, isn't worried about the drop-off in NFL TV audiences, which he attributed to the hurricanes. He told CNBC recently, "I think the NFL is still the best property on television."

Moonves' optimism is shared by Amazon (AMZN), which bought the rights to stream 10 NFL games this season. Once the league's broadcast deal expires, Weiser expects the e-commerce giant to bid along with other tech stalwarts such as Apple (AAPL) and Google parent Alphabet (GOOG). That might make an expensive business even more pricey for the media companies.