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 restaurant operator Darden Restaurants (NYSE: DRI) sank 10% on Tuesday after the company slashed its full-year 2012 outlook.

So what: Darden's cut was so big -- management now sees 2012 EPS growth of 4%-7% versus its prior view of 12%-15% -- that Wall Street has no choice but to lower its valuation estimates on the stock. Same-stores sales declines at its Olive Garden chain continue to hit Darden particularly hard, so it's no surprise that the shares are once again flirting with their 52-week lows.

Now what: I wouldn't be so quick to pounce on today's plunge. Margin-pressuring promotions, rising food costs, and lower traffic should continue working against Darden in the short term, while its clear lack of moat makes it an easy pass for the long term. Although they operate in the same fickle space, casual dining picks like Panera Bread (Nasdaq: PNRA) and Buffalo Wild Wings (Nasdaq: BWLD) can at least offer some tasty growth potential.

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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.