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 Gulfport Energy (Nasdaq: GPOR) have fallen 13% today in a wide sell-off of energy stocks.

So what: The oil sell-off has only gained momentum during the day and has now pushed oil down nearly 3% to $77 per barrel. There are worries about an economic slowdown in Europe as well as China feeding the massive sell-off today.

Now what: This story is starting to get old. Concerns about Greece have been driving the market for months, and today is no different. Greece won't meet deficit goals for bailout funds, which has sent the dollar higher and oil lower as a result. Lower oil prices means companies like Gulfport's shale plays will be much less profitable in the future if oil remains at depressed prices. That's weighing on investors' minds today.

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

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.

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.