Marissa Mayer fires Yahoo COO de Castro after just a year in the post

No direct reason given for CEO's 'difficult decision'

Yahoo's chief operating officer, Henrique de Castro, has been fired from the company, effective immediately, but with an estimated $40m severance package.

CEO Marissa Mayer revealed her decision via a memo to employees, which referred to her "difficult decision" after reflecting on 2013's company performance.

"During my own reflection, I made the difficult decision that our COO, Henrique de Castro, should leave the company. I appreciate Henrique's contributions and wish him the best in his future endeavors," said Mayer's memo, which also stated she is "proud" of Yahoo's 2013 accomplishments, and "optimistic" about what it will go on to achieve in 2014.

Mayer hinted that a leadership reshuffle will follow de Castro's ejection, explaining her belief that "these changes will enable even more successful execution".

De Castro had only been at Yahoo for a year and was one of Silicon Valley's most highly-paid executives. It remains a mystery exactly why de Castro is leaving, and what his next plans may be.

An ex-Google exec, like Mayer herself, de Castro was poached from Yahoo's rival soon after Mayer took control in mid-2012. Rumours of tensions between the two soon surface, however.

De Castro was chiefly in charge of advertising sales at Yahoo, tasked with building new relationships to help strengthen Yahoo's position in this area.

However, advertising is still a weak spot for Yahoo, with revenue falling seven per cent during 2013 when compared to its Q3 2012 figures, amounting to just £257m - or 40 per cent of the company's total sales.

After the announcement of de Castro's departure, Yahoo's share value fell by 0.6 per cent.