What: Shares of Greenbrier Companies Inc (NYSE:GBX) plunged another 20.7% in January, adding to the 39% the stock lost in 2015. The culprit in January was the company's 2016 guidance.

So what: Early in January, Greenbrier reported fiscal first-quarter results that were actually a record for the company. Revenue jumped 62% to $802.4 million, and net income was $69.4 million, or $2.15 per share. 

But investors were disappointed by just 500 new railcar orders during the quarter and by backlog falling from $4.71 billion to $4.14 billion in just three months. Even though earnings guidance of $5.65 to $6.15 per share was in line with what analysts expected, there was too much concern that falling oil prices would lead to weakened demand.

Now what: While falling backlog is a concern for any company, I think some context is needed with Greenbrier. Shares now trade at just 4.4 times 2016 earnings estimates, which is pricing the company as if it's going out of business. The balance sheet isn't too bloated, with just $488.6 million in debt, so if management can control costs while backlog decreases and pay down debt to reduce long-term risk, I think this could be a great entry point for investors. The rail business isn't going anywhere, and even though demand from energy companies may wane, the need for railcars will continue well into the future.

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.