SAN FRANCISCO: Yahoo chief operating officer Henrique de Castro, the high-profile recruit Chief Executive Officer Marissa Mayer poached from Google shortly after she took the helm, will leave on Thursday after about a year on the job.

Yahoo did not give a reason for his departure in a Wednesday filing, but in an unusually blunt memo to Yahoo staff obtained by the Recode technology blog Mayer said she had fired him.

"During my own reflection, I made the difficult decision that our COO, Henrique de Castro, should leave the company," Mayer wrote in the memo.

Yahoo declined to comment.

De Castro's departure marks a striking shift within Yahoo's leadership ranks as Mayer continues to struggle to revive the company's business one year-and-a-half into her tenure.

At the time of de Castro's hiring, Mayer was building a management team to try to revive flagging sales and traffic, and cited de Castro's Internet advertising expertise as a key asset. The Lisbon-born executive, known for tough talk and a strong personality, was richly rewarded with a compensation package totaling $58 million when he was hired.

The fact that Mayer managed to lure an executive from Google was viewed at the time as a sign that the new CEO had re-inspired confidence in the company.

But Yahoo's revenue growth has remained moribund. Revenue has declined between five percent and seven percent year-over-year in each of the first three quarters of 2013.

De Castro will get severance benefits as laid out in his October 15, 2012 employment letter, including equity awards, according to the filing. A source familiar with the matter said that part of the severance package is based on performance metrics which have not yet been determined or approved by the company.

De Castro could not immediately be reached for comment.

Yahoo is one of the world's most-visited online properties, but revenue has declined in recent years amid competition from Google and Facebook Inc. Mayer has built a senior leadership team and is now in the midst of engineering a turnaround at the once-dominant Web icon.