Declining NFL television ratings will lower CBS earnings, according to Credit Suisse.

The firm cut its third-quarter EPS estimates by 5 percent, citing CBS' softer Sunday NFL ratings. The media company reports on Nov. 2.

"We expect third-quarter network advertising to decline 3 percent (previously +1 percent), driven by soft ratings for both the summer schedule and for the start of the NFL season," wrote Credit Suisse analyst Omar Sheikh. "With only one of the three content licensing deals we expected for the second half announced in third quarter, we also expect content licensing revenue growth to be skewed to the fourth quarter."

Sheikh maintained his outperform rating and price target on CBS shares, which remains at $75, or 32 percent upside from Friday's close. He cut his third-quarter EPS estimate to $1.08, below Street consensus estimate of $1.12 from FactSet.

The analyst said CBS' Sunday NFL ratings are down 17 percent year over year during the first several weeks of the football season, according to the report. Sheikh released a similar report last week on Twenty-First Century Fox's earnings, which he also expects to disappoint thanks to weaker ratings by the NFL.

The stock has underperformed this year, falling nearly 11 percent since January and nearly 3 percent in the past month.

Shares of CBS were down 0.2 percent Monday.