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: Barely two weeks after a big rally fueled by an analyst upgrade, shares of Trina Solar (NYSE: TSL) fell more than 11% when peer First Solar (Nasdaq: FSLR) updated 2011 guidance and offered weak 2012 guidance.

So what: Investors fear that what's bad for one is bad for the other. They may be right. As my Foolish colleague Travis Hoium reported in October, burgeoning efficiency in solar module manufacturing is creating a supply glut, which in turns crimps sales and profits.

Now what: If history holds, we'll have to wait till February to get a fuller report on how Trina is navigating the delicate dance between progress and profits. What do you expect? Would you buy shares of Trina Solar at current prices? Let us know what you think using the comments box below.

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This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.