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 one month ago, ace investor UBS told investors to invest in Chicago Bridge & Iron shares (NYSE: CBI) -- which by the way, doesn't build a lot of bridges, and doesn't spend a lot of time working iron either. To UBS's way of thinking, the real reason to own this stock was its leading position in the "liquefied natural gas, gas processing, chemicals, and oil sands markets." But as energy prices continued to drift Tuesday, CB&I shares took a big hit, dropping as much as 10% before pulling out a "save" toward the end of the trading day.

So what: Why should you care? Well for one thing, because UBS is a pretty good stock analyst, ranked in the top 10% of investors we track at The Motley Fool's CAPS service. For another, because UBS spends more time analyzing oil and gas stocks than any other single type of equity.

Now what: For third ... when UBS told investors to buy CB&I back in August, the shares cost $35 and change, and UBS believed they were heading to $41, representing a 17% profit-tunity. Today, these same shares can be had for the low, low price of just $27 -- a potential 50% gain.

That's UBS's opinion, at least. But, for what it's worth, I agree with 'em (on the direction the stock's going in, at least). With a P/E of less than 12, and long-term growth rates estimated at 15% per year, CB&I shares look undervalued to me. Maybe not by 50% ... but definitely undervalued.

If I were you, I'd give 'em a looksee before Mr. Market comes to his senses.

Want to learn more about Chicago Bridge & Iron? Add it to your Fool Watchlist. There's more to this stock than bridges or iron.