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 specialty mattress company Select Comfort (NASDAQ:SNBR) plummeted 25% today after its quarterly results and outlook badly missed Wall Street expectations.

So what: The stock has rebounded nicely since its March lows on signs of recovering demand, but the third-quarter results -- income fell 23% on a revenue increase of just 7% -- coupled with downbeat full-year guidance reignite serious concerns over weak consumer spending. In fact, shares of close rival Tempur Sealy (NYSE:TPX), which will report in early November, are also sinking on the news as investors speculate on similarly weak results.

Now what: Management now sees full-year EPS of $1.14-$1.22, down from its prior view of $1.30-$1.45 and well below the average analyst estimate of $1.33. "[O]ur execution was muted by a progressively more challenged macro-economic environment, resulting in performance below expectations," said CEO Shelly Ibach. "Given the ongoing economic uncertainty, we are actively managing costs across the company, while continuing to support priorities important to long-term growth and profitability." More important, with Select Comfort shares off about 40% from its 52-week highs and trading at a forward P/E of 11, now might be an opportune time to bet on management.