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 casual-dining chain Ruby Tuesday (NYSE: RT) plunged 16% today after its quarterly results and full-year guidance disappointed Wall Street.

So what: Ruby Tuesday's third-quarter EPS managed to top estimates, but a big top-line miss -- revenue of $324.8 million versus the consensus of $339.0 million -- is triggering fresh worries over its long-term growth. According to management, the promotional environment continues to be highly competitive, suggesting that things aren't about to get better anytime soon.

Now what: Looking ahead, management now sees adjusted 2012 EPS of $0.43-$0.48, which is well below the consensus of $0.56. "While we are humbled by our sales and profit results this year," Chairman and CEO Sandy Beall said, "we are very excited about the future of Ruby Tuesday as we have solid plans that should allow us to leverage our strong free cash flow and balance sheet flexibility to grow our business and create value for our shareholders." However, given Ruby Tuesday's less-than-stellar fundamentals and shaky competitive position, I'd be cautious about buying into that optimism.

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