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 Harmonic (NASDAQ:HLIT) are down 8% today after dropping as much as 10% in early trading. The market reacted poorly to a mixed earnings report Harmonic issued last night, which offered underwhelming performance as well as little to get excited about for the current quarter.

So what: Harmonic's fourth-quarter revenue of $133.4 million was weaker than the $137.5 million expected, and the Street seems to have fixated on this underperformance rather than the $0.09 in adjusted EPS, which was a penny better than the consensus. For the current quarter, Harmonic expects revenue in the range of $115 million to $125 million, which comes in below the $133.3 million consensus estimate.

Now what: In last night's conference call, CFO Carolyn Aver pointed out that the first quarter's lowball estimate is the result of factors that aren't expected to carry through the full year. However, that doesn't excuse the company from having now issued five consecutive quarters of guidance anticipating year-over-year declines, in the words of Jefferies analyst James Kisner. Since this isn't an aberration, it may make more sense to watch this company instead of jumping in today. Nothing currently indicates that Harmonic is on the verge of a turnaround.

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Fool contributor Alex Planes holds no financial position in any company mentioned here. Add him on Google+ or follow him on Twitter @TMFBiggles for more news and insights. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.