The National Football League's weak viewership has Wall Street on edge, and the numbers don't look any better for Week 10.

Viewership fell 18 percent year over year in Week 10, which ended Monday, with lower ratings in all six game-time windows. JPMorgan analyst Alexia Quadrani noted that the slip in Week 10 puts the NFL's season-to-date audience decline at roughly 7 percent.

While that compares well with the NFL's 12 percent audience decline at this point in 2016, much of last year's showing was written off as a one-time effect from the presidential election. That may translate into some tough year over year comparisons for the NFL in the weeks ahead.

"Ratings are down in 8 of 10 weeks this season," wrote Quadrani. "We note that ratings picked up in 2016 starting in Week 10, which was the first post-Election Day slate of games. Total audiences were down only 3 percent post-election versus -12 percent through Week 9."

ESPN's "Monday Night Football" viewership fell 18 percent year over year during Week 10 after a 20 percent slip last week, while viewership of the late-afternoon national game on FOX featuring the Cowboys and the Falcons fell 24 percent, according to JPMorgan.

The National Football League did not immediately respond to CNBC's request for comment.

President Donald Trump contends that NFL television ratings have been down largely because of an ongoing controversy over players kneeling during the playing of the national anthem.

Tweet Link

The weak viewership numbers are taking a toll on media companies, from Wall Street's perspective.

Just last month, Credit Suisse's Omar Sheikh cut earnings expectations at CBS, explicitly citing soft Sunday NFL ratings. In CBS's third-quarter earnings report earlier this month, Chairman and CEO Leslie Moonves briefly addressed the concerns, but still called the NFL a "great product."

"Look, the NFL, obviously there's been a lot going on. The ratings are down a bit this year," he said. "There's been a lot of talk on it. Obviously, there were political issues that came up about kneeling during the anthem, and it became very controversial."

"But once again, we're still happy we have the NFL."

Credit Suisse's Sheikh also lowered his price target and earnings per share forecasts for Twenty-first Century Fox, citing Fox's poor Sunday NFL ratings on Oct. 12.

"NFL ratings [are] weak so far," he wrote. "This was negatively impacted during the first 2 weeks by hurricane disruption, but is disappointing given the soft comps – if ratings do not improve materially, we see a potential headwind to domestic advertising revenues in Q2/Q3 '18."

Correction: An earlier version misspelled analyst Alexia Quadrani's last name.