Google shareholders are reckoning with an unfamiliar concept to start 2015: Downgrades.

Analysts at Stifel Financial and Atlantic Equities dropped their "buy" ratings on Google this month ahead of fourth-quarter earnings, which the Mountain View, California-based company will report after the closing bell on Thursday. The percentage of analysts with "buy" recommendations on the stock fell in January to 79 from 84 in December, the first monthly decline in bullishness since November 2013, according to FactSet.