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 rehab specialist and hospital operator Rehabcare Group (NYSE: RHB) dove nearly 12% in intraday trading as investors reacted to the company's third-quarter earnings report.

So what: Rehabcare, which competes with larger players such as HealthSouth (NYSE: HLS) and Select Medical (NYSE: SEM), showed some pretty decent numbers for the third quarter. Overall, the company's revenue and earnings soared 65% and 131%, respectively, from last year, though, most of that gain was from the acquisition of Triumph HealthCare. Excluding Triumph, revenue was up 11%. Total earnings per share of $0.64 met the average Wall Street estimate.

Now what: While the current-quarter results don't sound all that bad, the sharp reaction of investors today is likely because of the company's fourth-quarter guidance. Rehabcare doesn't provide an earnings-per-share number for analysts to back their models into, but instead gives guidance for various metrics in each of its businesses -- and none of those metrics looks particularly promising. The company expects margins will likely contract and that top-line growth may be nonexistent. Analysts' may now update their estimates based on the company's guidance, but based on current 2010 estimates, Rehabcare's stock is trading at a price-to-earnings multiple of less than nine. While the fourth quarter may not be stellar, that price tag could make this stock worth a closer look.

Interested in more info on Rehabcare? Add it to your watchlist by clicking here.

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.

Fool contributor Matt Koppenheffer does not own shares of any of the companies mentioned. You can check out what Matt is keeping an eye on by visiting his CAPS portfolio, or you can follow Matt on Twitter @KoppTheFool or on his RSS feed. The Fool's disclosure policy assures you no Wookiees were harmed in the making of this article.