Could the country’s third largest wireless carrier Sprint be headed toward a bankruptcy filing? That’s the fear of at least one stock analyst who said the company — led by telecom vet Dan Hesse and a big backer of Clearwire — faces a very uncertain future. The stock continued to fall today, down another percentage point with Sprint now showing a market value of $8 billion.

Bernstein Research analyst Craig Moffett said the company faces too different paths in the next two years. “In the first, the company successfully navigates its complicated Network Vision upgrade, stabilizes Clearwire’s financial position, and delivers a compelling 4G product,” Moffett wrote. “In the second, some combination of its gargantuan take-or-pay contract with Apple, a hobbled 4G offering, and a stupendous debt burden bring the company to its knees.”

Sprint Nextel’s stock fell 4.5 percent Monday on the news. Moffett said he’s not predicting a bankruptcy filing, but he raised it as a possibility. Other analysts contacted by Reuters said that the risk of bankruptcy is rather small, even though the company does face looming debt payments and increasing costs related to its $7 billion network upgrade.

Sprint has lost 85 percent of its value in the past five years. Hesse, the former CEO of Redmond-based TeraBeam and AT&T Wireless, has served as CEO of Sprint since December 2007.

[Hat tip to Fierce Wireless]