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 convenience store operator Casey's General Stores (Nasdaq: CASY) fell 10% today after earnings were released and the company was downgraded by an analyst.

So what: Revenue of $1.37 billion beat estimates of $1.29 billion, but that didn't translate to profits on the bottom line in the fiscal third quarter. Adjusted earnings per share were $0.37, below estimates of $0.50. Analysts at Feltl & Co. also downgraded the stock from a strong buy to just a regular buy, although that has just helped a move that was already coming.

Now what: Management blamed higher credit card fees and insurance for the 18.5% rise in operating expenses that hurt profit. The company has also been adding stores at a rapid pace, and bringing them into the fold has been more expensive than expected. Considering the company's expansion and today's discount, I see this as a buying opportunity for investors.

Interested in more info on Casey's General Stores? Add it to your watchlist.

Fool contributor Travis Hoium does not have a position in any company mentioned. You can follow Travis on Twitter at @FlushDrawFool, check out his personal stock holdings or follow his CAPS picks at TMFFlushDraw.

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