That has prompted analysts to steadily reduce revenue estimates. In the last six months, consensus estimates for 2015 revenue have fallen 7 percent to $14.5 billion. In a turbulent market, estimate revisions are likely to spook investors who are watching the advertising market closely.
There's reason to believe TV could lose more ad dollars to digital media over time. Some 38 percent of media consumption occurred on television in 2013, while TV accounted for 45 percent of advertising spending, according to Guggenheim Partners analyst Michael Morris, who cites data from advertising firm WPP.
Of course, CBS continues to carry some of the best content available, which should continue to attract advertisers. Its new shows for the fall season such as "Scorpion" and "Madam Secretary" have performed nicely and could well go on to additional seasons, said Anthony DiClemente, an analyst at Nomura. CBS also has huge amounts of exclusive sports content—including the new Thursday night football.
But barring an enormous ratings surprise, CBS may have a tough time turning advertising trends around completely. That may leave investors focused on other growth levers the company can still pull over time.
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One strategy that has helped CBS immensely in the last several years is charging so-called retransmission fees from cable and satellite companies. Retransmission fees are a payment CBS receives from those companies for the right to air its content.
But while CBS has forecast $2 billion in annual retransmission fees by 2020, it may be difficult to impress investors with a bigger number anytime soon. Michael Nathanson of research firm MoffettNathanson said a large portion of the company's retransmission deals are already locked up through 2020 and the growth trajectory is well understood.
Showtime, CBS' premium pay-TV network, should also drive growth over time. The network had 22.5 million subscribers at the end of the second quarter compared with 30.4 million for rival HBO, a unit of Time Warner. Showtime also charges subscribers less per month, suggesting there's upside over time if the network keeps rolling out hit originals.
CBS is keeping up with changing viewer habits. The company announced Thursday that it will offer "CBS All Access," which gives viewers the ability to watch any content from the CBS broadcast network through its website. CBS will charge $5.99 a month, income that should carry a very high margin since it already owns the digital rights to its content.
The more immediate way CBS can get the attention of investors: share buybacks. In 2015, consensus estimates reflect just 6.6 percent growth in earnings before interest, taxes, depreciation and amortization. But with the help of buybacks, analysts expect earnings per share to rise 21 percent.
The advertising market could keep CBS shares beaten down for some time, especially if advertising trends worsen. But with steady sources of growth, the share buyback could pack a dangerous punch against anyone betting against the stock.
UPDATED: This story was updated to include news of CBS' new "CBS All Access" service.