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 Key Energy Services (NYSE: KEG) fell as much as 19.5% today after the company lowered second-quarter guidance.

So what: Key said that revenue was expected to grow 5% to 7% compared to the first quarter, down from a previous expectation of 10% to 15% growth. Earnings from continuing operations are now expected to be $0.18 to $0.20 from a previous expectation of $0.31 to $0.33.

Now what: Lower activity in the natural gas market was blamed for the lowered expectations, which will affect the fluid management, coiled tubing, and rental services businesses. The rig services business is expected to do well as liquids production in the U.S. remains high. Estimates will probably need to come down for 2012, but it looks like the stock has already priced in some bad news. Shares trade at just 5.9 times the current estimates, and even if they're lowered some, the stock is reasonably priced.

I think long-term activity will pick up in both natural gas and liquids and the stock will move higher from this latest low.

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