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 data backup company Quantum (Nasdaq: QTM) fell 18% today after reporting weak earnings.

So what: Adjusted earnings of $0.07 per share didn't meet analysts' expectation of $0.09, causing the drubbing today. Investors were also confused by management's explanation of order delays from the third quarter and also its weak outlook in the fourth quarter, when delayed orders should come through.

Now what: The trouble closing deals is troublesome, but the lower-than-expected guidance should be the biggest concern going forward. Guidance of $0.04 to $0.05 was half of analysts' expectation of $0.09, and those lower expectations will weigh on the stock. I am selling today's move and will have to see some improvement before I want to jump into this stock.

Interested in more info on Quantum? 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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