Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

While the Dow may have been able to squeak by with meager gains Friday, the S&P 500 Index (^GSPC -0.71%) wasn't so lucky. Telecom was the worst sector in the stock market today, but three of the most severe decliners came from tech and basic materials. At the end of the day, stocks were torn, tugged higher by a Federal Reserve committed to quantitative easing, and pulled lower by December auto sales that failed to impress. The S&P ended the day down 0.6 points, or less than 0.1%, to end at 1,831. 

Investors in today's three laggards certainly wish their stocks had been as indecisive as the broader market Friday; Peabody Energy (BTU), for instance, ended as the index's most substantial decliner, losing 3.9%. A coal miner, Peabody Energy mines for both thermal and metallurgical coal, selling its product to utilities providers and titans of industry alike. Peabody could be in a prime position to benefit should natural gas prices continue to rise, as energy consumers switch to a more cost-efficient coal. Natural gas isn't far off from 52-week highs, but Peabody didn't catch any breaks today, as natural gas prices actually fell slightly.

Far away from the coal mines, shares of Micron Technology (MU -2.72%) fell 3.2% today after the stock was downgraded by RBC Capital, which cited valuation concerns as the reason for its newly unenthusiastic outlook. The chipmaker could indeed be in for tougher times if monster customer Apple decides to scale back purchases of Micron Technology's dynamic random access memory, or DRAM, products. Apple -- a company worth nearly half a trillion dollars -- is more than 20 times larger than Micron, and certainly has the upper hand in the leverage game.

Lastly, shares of Cliffs Natural Resources (CLF -2.51%) shed 3% today, driving home the point that it was truly a bad day for coal miners. Cliffs Natural Resources can in some way be seen as a derivative play on steel prices, since its two big focuses are iron ore and metallurgical coal, key ingredients in the metal's industrial production. While Goldman Sachs sees global steel consumption rising nearly 5% this year, these projections haven't meant much to Cliffs Natural, which has gotten off to a rough start in 2014.