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 Standard Motor Products (NYSE:SMP) weren't looking up to snuff today, falling as much as 10% today after Goldman Sachs downgraded the entire U.S. auto sector and lowered its rating on Standard form "neutral" to "sell."

So what: The investment bank dropped its rating on the entire industry from "attractive" to "neutral," primarily on rising interest rates, which could affect borrowing for auto loans. Goldman noted that auto stocks have underperformed the S&P 500 by an average of 26% in three of the past four periods of rising interest rates. The downgrade weighed on much of the auto industry, as Ford fell 3.1% and General Motors 0.9%, but Standard, which makes replacement parts for the aftermarket industry, took its downgrade particularly hard.

Now what: Considering Standard serves the automotive aftermarket, which should not be affected as much by any immediate decline in demand, it's surprising to see shares tumbling like this. Goldman cited valuation concerns and potential earnings deterioration for slapping a sell rating as shares of the company had nearly tripled in the past year. Still, a drop like this on a simple downgrade seems exaggerated, and shares are still modestly valuated. Notably, shares closed less than $1 away from Goldman's $34 price target. I'd expect at least some of today's loss to be recovered in the coming weeks. 

Fool contributor Jeremy Bowman and The Motley Fool have no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools don't 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.