Yahoo shares dipped 0.7 percent in after-hours trade to $32.58.
The stock has tumbled as much as 40 percent from highs early this year amid skepticism over Yahoo's ability to regain its prominence in the tech sector.
To make matters worse, Yahoo has lost a number of key executives, including development officer Jackie Reses marketing executive Lisa Licht, who departed this week.
A key to Yahoo's future is how it handles the cash from its stake in Alibaba and reshapes its core operations.
Mayer said the company is making "good progress" toward its goal of completing the deal by the end of the fourth quarter but noted that with regulatory issues and holiday delays, "the transaction may ultimately conclude in January."
Yahoo in July formally notified US regulators that it is spinning off its stake in Chinese e-commerce giant Alibaba to an independent new company called Aabaco Holdings.
Aabaco will wind up owning approximately 384 million shares of the Alibaba Group, representing an interest of about 15 percent.
Early in September, the Internal Revenue Service refused to promise that the Internet pioneer's plan for spinning off its Alibaba holdings would sidestep US taxes.
The IRS declined a request for a preliminary ruling that the way the spin-off is structured satisfies requirements for avoiding taxes on the stake in Alibaba. At the same time, the IRS did not indicate for sure that the transaction would be taxable.
The tax treatment could mean billions for Yahoo, whose market value is seen as minimal after discounting the stakes in Alibaba and Yahoo Japan (Other OTC: YAHOF - news) .