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 auto replacement parts manufacturer Standard Motor Products (NYSE: SMP) sank 15% on Tuesday after its quarterly results and guidance missed Wall Street expectations.

So what: Standard Motor's fourth-quarter earnings were pretty much in line with estimates, but a miss on the top line -- $174.2 million versus the consensus of $181.5 million -- is triggering concerns over slowing demand. Of course, the stock has been on fire over the past several months, up about 130% from its August lows, so a hiccup shouldn't come as too big of a surprise.

Now what: Looking ahead, management sees current-quarter revenue of $220.2 million, also below Wall Street's estimate of $232.9 million. "On balance, we are optimistic heading into 2012," said Chairman and CEO Lawrence Sills. "The positive industry demographics will continue (though, in the near term, these may be inhibited by the rise in gasoline prices)." Given the stock's still-reasonable forward P/E of 12, betting on those long-term tailwinds might be worth looking into

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