In the fast-growing Russian internet scene, one of the big three portals, Rambler, could be about to lose its CEO, after dropping market share and seeing the sale of its advertising unit to Google (NSDQ: GOOG) fail. Mark Opzumerom won’t renew his contract, which ends in March, after Rambler.ru’s share of Runet’s search market fell from 14.9 percent last year to just 6.4 percent, business paper Vedomosti says (via Yakov).

SEE ALSO: Russian Portal Rambler Lays Off 50 Percent Of Staff After Blocked Google Deal: Reports

Rambler had agreed to sell its Begun contextual advertising platform to Google for $140 million in a summer deal that would also have seen Google replace Rambler’s own on-site search box. But the acquisition was curiously blocked in October by Russian antitrust authorities, arguing Google had not supplied the necessary paperwork. Google has already moved on and is testing the provision of search to leading social net Odnoklassniki. An exit for Opzumerom may suggest the Begun-Google deal may not be revisited.

Meanwhile, in a second blow to Google in Russia, the Firefox browser has picked Yandex to be the default search box service in Russian versions of its forthcoming 3.1 release - a move that will swell Yandex’s search traffic and ad views at the expense of Google, Firefox’s regular search provider. Mozilla general counsel Harvey Anderson wrote users “really wanted direct access to the Yandex search”.