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 action sports apparel retailer Zumiez (NASDAQ:ZUMZ) plunged 10% today after its quarterly results and guidance disappointed  Wall Street.

So what: The company's third-quarter EPS managed to top estimates, but a 4.2% same-store sales decline in November, coupled with downbeat guidance for the current quarter, is forcing analysts to lower their valuation estimates yet again. Management cited softer-than-expected sales trends in Europe for the disappointing results, but even more worrisome to Wall Street is how quickly the brand is losing its appeal here at home.

Now what: Management now sees fourth-quarter EPS of $0.59-$0.62 on revenue of $218 million-$221 million, versus Wall Street's view of $0.71 and $222.9 million. "[W]e are confident that the key components of our long-term growth strategy will allow us to profitably expand our share of the global action sports lifestyle market and deliver increased value to our shareholders," CEO Rick Brooks reassured investors. Of course, when you consider the strong economic and competitive headwinds that continue to work against Zumiez, betting on that bullishness seems particularly risky.

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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.