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: RPC Inc. (NYSE: RES) shares fell 10% today after Goldman Sachs (NYSE: GS) initiated coverage on the company with a sell rating.

So what: The oil and gas service provider has been on a big run-up lately, but Goldman thinks the run is over. The analyst said, "We expect capacity additions and a flattish rig count to cause margins to peak in 2Q 2011," and it is time to get out of this cyclical stock.

Now what: It may be time for this stock to take a breather after shooting up 139% since the beginning of June. But financial performance has improved so much over the last year that I would like to see real weakness in earnings before giving up all together. Today I'll sit on the sidelines, but a further pullback could be a nice entry point for this stock.

Interested in more info on RPC Inc.? 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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