NEW YORK (TheStreet) -- Viacom's (VIAB) - Get Report already-struggling shares could plunge even further if Dish Network (DISH) - Get Report doesn't renew its contract to carry the company's networks including MTV and Nickelodeon.

That's the sobering message about New York-based Viacom from Bernstein analyst Todd Juenger as shares in the media company fell another 4% to $43.90 on Friday, extending its 2015 decline to 43%.

"The market is also building in some probability of a much worse downside scenario, triggered by the potential loss of traditional distribution, starting with Dish," Juenger wrote in an investor note Friday, setting a new price target of $42 per share and an underperform rating. "The Dish renewal is a very binary event. If Dish renews, VIAB stock will go up. If Dish does not renew, VIAB stock will go down (a lot)."

Dish, with its Viacom deal set to expire this year, provides Viacom with 14 million subscribers and cable channels including Comedy Central. Under Bernstein's analysis, if Viacom doesn't retain Dish, its shares could plunge to $28. On the other hand, Juenger expects shares to rise to $51 if Dish does renew.

Juenger said Viacom CEO Philippe Dauman will "quickly face hard choices" if Dish drops and he estimates a roughly 40% chance that Dish won't renew its so-called carriage agreement with the company. Juenger was quick to add that forecasting the exact figure of a decline was difficult to calculate but that "it's higher than 20%."

Viacom officials had no comment on Juenger's report.

Viacom, Juenger said, is vulnerable to a cancellation because it "stands out as expensive relative to its peers" and offers much of its content on digital platforms. Additionally, Dish needs to differentiate its service as a "value" provider with a lower cost structure, so cutting programming is something that Dish is likely to pursue.

But Dauman certainly has an argument to make for retaining Viacom. Namely, if Dish were to drop Viacom, it would likely lose subscribers. Pay-TV is Dish's only operating business so it can't make-up for lost revenue through alternative channels like broadband, Juenger emphasizes.

"Going into the Dish renewal, frankly we'd be nervous on either on the long or short side of VIAB," Juenger said. "It is a hard-to-predict binary event, and the stock will move significantly up or down."

While Viacom earlier this year lost deals with smaller cable operators like Cable One and Suddenlink over disputes over distribution fees, Viacom still holds tight to larger deals with Comcast (CMCSA) - Get Report and Time Warner Cable (TWC) .

Viacom shares were also bruised along with most media stocks amid broad declines in advertising revenue and consumer trends away from larger cable bundles and increased online viewing through outlets led by Netflix (NFLX) - Get Report.

Pay-TV distributors are going to want to pay less to the networks in coming years to carry their programming given that fewer people are watching, Morgan Stanley analyst Benjamin Swinburne said in a note last week, cautioning against buying media stocks on the recent sell-offs, fueled in part by Walt Disney (DIS) - Get Reportreporting it had lostESPN customers.

The pay TV industry lost 566,000 subscriptions from April through June with the sector now declining at an annual rate of 0.7 percent, according to MoffettNathanson analysts. That compares to 0.1% declines a year prior.