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 oil and gas producer Newfield Exploration (NYSE:NFX) fell 15% today after reporting earnings.

So what: Third-quarter revenue fell slightly to $615 million, below estimates of $652 million. Adjusted earnings per share were $0.48, just below estimates of $0.51.

What the adjusted results don't include is a $135 million derivative loss, which swung the company to a $33 million loss.

Now what: Management also said that international production may be down 25% next year, which appears to be getting a lot of investor attention. I'm looking at the GAAP loss of $33 million as a great reason to sell today and will overlook the adjusted results. Many companies continue to lose their shirts on derivative "hedges" and I don't like exposure to these kind of losses.

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Fool contributor Travis Hoium has no positions in the stocks mentioned above. The Motley Fool has no positions in the stocks mentioned above. 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. The Motley Fool has a disclosure policy.