(REUTERS) - Activist investor Starboard Value is raising expectations a proxy fight could be brewing at Yahoo.

In a letter to Yahoo's board of directors, Starboard urged the company to separate its Asian assets and sell its core Internet business. Without naming CEO Marissa Mayer directly, Starboard also called for change at the top, writing: "Yahoo's current management has had over three years to demonstrate progress towards improving the Core Business, but despite these efforts, the Core Business continues to be plagued with deteriorating financial performance."

But management changes have failed in the past warns Reuters Breaking Views' Jen Saba.

"Yahoo has had I believe six or seven chief executives in the past decade," she said.

"They just keep shuffling through management. So, at this point, to come in and say we need a new CEO just seems like one more step backwards. What I think needs to happen is that Yahoo should probably be sold while it still has value and probably be subsumed into a larger corporation."

Starboard owns less than 1 per cent of Yahoo. But Ms Saba says many other investors are also unhappy with the company's performance.

Meridian Equity Partners' Jonathan Corpina points to the stock, which has lost about 35 per cent in the past year.

"It gets to a point where you've got a performance in a stock like Yahoo that has been down over a period of time with other factors that have added into that. Yes, large investors will ask some hard questions and ask for some change at the management level," said Mr Corpina.

Yahoo said in a statement it will share its plans for creating a more focused company on or before its earnings call on Jan 26.