By Alexei Oreskovic SAN FRANCISCO (Reuters) – Yahoo Inc chief operating officer Henrique de Castro, the high-profile recruit Chief Executive Officer Marissa Mayer poached from Google Inc 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.