Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of Yandex NV (NASDAQ:YNDX) fell as much as 12% early Tuesday, then partially recovered to trade down around 5.2% as of 11:30 a.m. after the leading Russian search engine reported solid first-quarter results, but followed with disappointing guidance.

So what: Quarterly revenue climbed 13% year over year to 12.3 billion Russian rubles (RUR), or $211.1 million, which translated to a 12% decline in adjusted net income to 2.2 billion RUR, or $38.5 million. On a per-diluted-share basis, adjusted net income fell around 18.8% to 6.61 RUR, or $0.11. Analysts, on average, were anticipating adjusted net income of 6.18 RUR per share on roughly the same amount of revenue.

However -- and with the caveat that guidance is limited to a quarterly basis due to the current macroeconomic situation in Russia -- Yandex currently expects revenue for the current quarter to grow just 9% to 12% over the year-ago period. Wall Street was modeling growth near the high end of that range.

Now what: It doesn't help that three months ago, Yandex told investors to expect higher first-quarter revenue growth of 15%. Falling short of that guidance today doesn't exactly leave investors optimistic for Yandex's chances of hitting the high end of its current range. And though Yandex is still the undisputed search leader in Russia with a 58.6% share of the market, it appears to have continued giving up ground to Google as this marks another sequential decline from 59.7% last quarter, 60.3% in Q3 of 2014, 61.6% in Q2 2014, and 61.9% in the year-ago period.

Investors should also keep in mind Yandex filed an antitrust complaint against Google almost three months ago, alleging Big G has engaged in anti-competitive practices including preventing pre-installation of Yandex services on Android devices. In the end, though, given its continued market share losses and Google's relative experience in defending its actions in court, I'm content watching Yandex's story unfold from the sidelines for now.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.