Fresh trouble is brewing in Yahoo after an activist investor group, Starboard Value, called up the shareholders on Thursday to take the lead in overseeing a “turnaround plan, separation, or sale of assets.”  The call implies parting ways with CEO Marissa Mayer and replacement of the entire company board.

For Mayer, who took over in July 2012, this will be the latest challenge.  The current board includes Mayer and the company co-founder David Filo.

The timing of the investor group’s rebellion is significant. Yahoo has been looking for buyers to sell off its core online business including search, mail and news sites, reports CNet.

Starboard’s letter to the shareholders said Yahoo is deeply undervalued and “opportunities exist within the control of management and the Board of Directors to unlock significant value for the benefit of all shareholders.”

Mayer is a former Google executive and has been taking many steps to make Yahoo competitive vis a vis the rivals, including Facebook, Google and Snapchat.

In February, Mayer cut 1,700 jobs and invited would-be buyers, saying she and Yahoo’s board are ready to “engage on qualified strategic proposals.”

Starboard, which owns 1.7 percent of Yahoo, wants its own members on the board as a replacement when the annual shareholder meeting is held in June 2016.

“We cannot envision a scenario where the shareholders of Yahoo would entrust the current management team and Board with executing a standalone turnaround plan given the years of failed attempts under the current leadership,” Starboard wrote.

Yahoo still claims a large audience of one billion visitors but is unable the monetize the big audience suitably. Meanwhile, Yahoo stated that it would review Starboard’s nominees and respond in due course, reports Reuters.

However, some analysts said Starboard’s plan of “board grabbing” may not be easy as chances of an agreement between Yahoo and Starboard are still bright. Even in a shareholder vote, the outcome may be decisively influenced by the votes of many mutual and index funds..