Yahoo! Inc. said Chief Operating Officer Henrique de Castro is leaving, little more than a year after Chief Executive Officer Marissa Mayer hired him from Google Inc. to help revive growth at the struggling Web portal.

De Castro’s departure, the first high-profile exit of an executive Mayer recruited, is effective Thursday, the company said Wednesday in a filing with the U.S. Securities and Exchange Commission. He will receive severance benefits and equity awards in line with his contract, Yahoo said.

Mayer, who took the helm in July 2012, has been working to reinvent Yahoo by revamping products and adding exclusive content to help it compete with Google and Facebook Inc. for users and advertisers. New products, redesigned e-mail and a spending spree on startups, engineers and media figures so far haven’t translated to growth. Analysts project that the Sunnyvale, California-based company’s revenue dropped 1 percent in 2013, with a 3 percent gain estimated for this year and next, according to data compiled by Bloomberg.

Yahoo’s share of the U.S. digital-advertising market is estimated to shrink to 5 percent in 2015 from 5.8 percent last year, while Google and Facebook both may expand their shares, to 42 percent and 9 percent next year respectively, according to EMarketer Inc.

Before joining Mayer at Yahoo, de Castro was vice president of Google’s partner business solutions worldwide. When his move was announced in October 2012, he was granted a pay package at Yahoo worth as much as $61.6 million over four years, including as much as $20 million in restricted stock units to compensate him for leaving Google, where he worked since 2006, according to a company filing.