Charter Communications just wrapped up its acquisition of rival Cox Communications. Sealing the deal isn't cheering up Charter's depressed stock.

On Thursday, Charter announced that it had acquired privately held Cox, first announced last year, creating the nation's largest internet and video provider by subscriber base. Charter now has 37 million customers-Cox's six million and its 31 million.

Charter also said it had completed its acquisition of Liberty Broadband, agreed to in 2024.

The deals didn't lift the stock, though. It was down 4.7%, bringing losses to 30% this year.

Scale alone isn't enough for shareholders. They're worried about subscriber losses-wireless carriers are grabbing customers-as well as Charter's significant debt load.

The risk is that Charter-in adding Cox to its business-is exposing itself more to the same pressures it already faces.

BNP Paribas analyst Sam McHugh estimates Cox's subscriber base is falling by 5% a year.

"Cox is facing intensified competitive pressure in the broadband space following the deal announcement...and the efficiency of cost-cutting as a driver for Ebitda [earnings before interest, taxes, depreciation and amortization] growth appears to be waning," wrote McHugh.

What could help Charter is some sort of a deal with Comcast, which Wall Street has talked a lot about. Analysts used to think it was a long shot because of antitrust issues, but now they now see it as more realistic because of Comcast's internal restructuring and growing competition from wireless and satellite internet.

"While we believe a Charter-Comcast deal is likely over time, we do not anticipate one imminently," wrote Sebastiano Petti, a J.P. Morgan analyst. "Charter will first need to begin integrating Cox, including the launch of new pricing and packaging, stabilize subscriber and financial KPIs [key performance indicators]...before entertaining a combination."