In the face of diminishing revenue from ad sales at the hands of rivals Google and Facebook, Yahoo Inc., has hired management consulting firm McKinsey & Co. to help with the reorganization of its core businesses.

McKinsey will help Yahoo decide which units to shutter, sell or invest in, according to Re/code, citing various people familiar with the situation. 

Under Chief Executive Marissa Mayer, Yahoo! has been trying to revive its core media and online advertising businesses by spending more to get users on its websites. However, this strategy has seen little success.

After deducting the fees paid to partner websites, Yahoo's revenue dropped to $1.0 billion in the third quarter from $1.09 billion a year earlier, and the company expects the trend to continue with a forecasted drop to $920-960 million in the current quarter, according to Reuters.

As the company continues to struggle to find its footing, high-level employees' morale is at an all-time low. Several top executives, including Media head Kathy Savitt and Chief Development Officer Jackie Reses, have left in the last couple of months, and Yahoo insiders expect at least two people who report directly to Mayer to leave the company.

In light of this, Mayer has asked top executives over the last month to make a three to five-year commitment to Yahoo, according to The Street.

Yahoo shares were down about 1.4 percent at $33.72 in early trading, continuing a trend which has seen Yahoo's stock plummet by about 32 percent this year.