Financially troubled Lehman Brothers reportedly faces a new challenge – the threat of mass defections by staff who fear a major new round of layoffs.

Unnamed Lehman executives view a sale of the bank as the main alternative to cutting loose as many as 5,000 of its 26,000 employees, according to CNBC.

"Already fear is spreading through the senior ranks of the investment bank: Worried bankers and traders have recently been making frantic calls to better capitalized banks, like Credit Suisse and others in hopes of landing jobs before the cuts come," the network's story says.

Wall Street headhunter Jay Gaines told eFinancialCareers News he's had few calls from candidates looking to jump from Lehman. For recruiters, "The Street talent today is a prime target across the board," said Gaines, the chief executive of Jay Gaines & Co. "There's the most vulnerability at Lehman. But we haven't seen people at Lehman panicking and calling en masse."

According to CNBC, Lehman Chief Executive Richard Fuld is thought to be pursuing potential bidders that include HSBC, Barclays, Toronto Dominion and Blackstone.

While Fuld reportedly has no "concrete plan" for further job cuts, unnamed Wall Street executives told CNBC that major layoffs are inevitable unless the bank is sold to a bigger player or business suddenly improves. Lehman already has reduced its headcount by 10 percent since the beginning of 2008.