Just as we examine companies each week that may be rising past their fair values, we can also find companies trading at what may be bargain prices. While many investors would rather have nothing to do with stocks wallowing at 52-week lows, I think it makes a lot of sense to determine whether the market has overreacted to a company's bad news, just as we often do when the market reacts to good news.

Here's a look at three fallen angels trading near their 52-week lows that could be worth buying.

Get your motor running
I generally recommend avoiding companies that are losing money, because red ink is often more than enough to justify a 52-week low. But exceptions can be made.

This week we'll start off with Westport Innovations (NASDAQ:WPRT), a company that supplies technologies to original equipment manufacturers in the automotive industry that'll allow engines to run on natural gas or liquefied natural gas.

On paper you can quickly see the allure of such a technology. The U.S. government has set fairly strict fuel-efficiency standards over the coming decade that need to be met in order to conserve natural resources and also reduce greenhouse gas emissions, which could harm the environment. The short story is that the abundance of natural gas via a number of new shale discoveries over the past decade could make for the perfect scenario to introduce more vehicles powered by natural gas and LNG. Natural gas is cheaper and cleaner than traditional fossil fuels, offering Westport Innovations multiple avenues for growth.

Of course, not all skeptics see it this way -- and I should know, as I was one of them for a while. Although it's developing this disruptive technology, Westport has to contend with large hurdles like minimal infrastructure (you won't find a CNG or LNG fueling station on every corner), increasing competition, and ongoing losses as it slowly introduces and validates its technology. What this means for shareholders is the potential for future dilutive secondary offerings made to raise cash for research and development and Westport's ongoing business expenses.

Now, though, could be the time to consider tapping the gas on Westport. Aside from its proprietary technology, Westport's greatest asset is its partnerships, especially with heavy-duty engine manufacturer Cummins (NYSE:CMI). The two have been collaborating on natural-gas-powered engines for years in the trucking industry, and with diesel prices again rising, the need for clean-burning and cheap fuel solutions has never been greater.

Westport also acquired BAF Technologies and a number of other subsidiaries last year in order to strengthen its ties to red-hot automaker Ford, assisting its consumers with natural-gas vehicle conversions.

While profitability could still be two or three years off, I consider these partnerships to be worth their weight in gold. For that reason I'd suggest digging deeper into Westport Innovations.

Hitting the Threshold
I'm not actually going to break my rule twice in the same week and present another company losing money that you should consider...am I?

You bet I am.

Up second this week is clinical-stage biopharmaceutical company Threshold Pharmaceuticals (NASDAQ: THLD), which has been crushed along with the rest of the biotech sector lately. The recent dip in Threshold shares has more to do with a lack of catalysts these days than anything else. The last exciting news investors got came in December, when Threshold described intriguing preliminary results from an early-stage study involving TH-302 in advanced multiple myeloma patients. Since then, however, its share price has vacillated without much direction. 

The promise of Threshold Pharmaceuticals lies with its lead drug TH-302. This unique therapy targets areas of tumor hypoxia, or areas of low oxygen. You see, normal cellular growth is often controlled and structured, with blood vessel growth keeping pace with normal cells. In sum, there are few instances of cell hypoxia. Tumors, though, grow willy-nilly and often outpace blood vessel growth, leaving some areas of the tumor with few blood vessels and little oxygen. TH-302 hones in on these areas and attacks, giving it the opportunity to destroy cancer cells with minimal healthy-cell death.

Threshold's experimental therapy is currently being tested in a combination of nine company-run and investigator-sponsored trials covering a gamut of cancers ranging from soft-tissue sarcoma and various types of leukemia to pancreatic, kidney, and liver cancer.

The downside, as you may have noticed, is that with the exception of midstage diagnostics therapy 18F-HX4, currently in a phase 2 study, Threshold's entire pipeline is dependent on TH-302. This means a failure in one of its late-stage studies (soft-tissue sarcoma or pancreatic cancer) could hurt investor perception of success. But investors should also keep in mind that different cancers can respond very differently to the same drug, so a failure in one study might be followed by wild success in another.

Thus far, data suggests that TH-302 offers a notable clinical benefit to patients. In its phase 2b pancreatic cancer study TH-302 was associated with a 41% reduction of risk for disease progression or death, ultimately improving progression-free survival by 2.4 months. Its ongoing phase 3 MAESTRO trial for pancreatic cancer will be a huge upcoming catalyst for this stock -- and I suspect it will be a positive one. 

Black gold
I figure I have to give you at least one currently profitable company to dig into: Rowan Cos. (NYSE:RDC).

Rowan joins the parade of offshore oil and gas contract drillers that I've listed here over the past couple of months that have struggled under the weight of tighter offshore spending and the prospect of newly introduced drilling vessels throughout the sector, tightening day-rates. The result has been lower-than-expected operating efficiencies throughout the sector.

Rowan has also dealt with a number of other issues, including the extended downtime of its Gorilla VII rig, which was damaged while being moved last year. In its March fleet status update, Rowan also notes that Gorilla V and Gorilla VI would have downtimes that are higher than previously expected for maintenance and inspections. In its latest quarterly results, Rowan also blamed poor weather conditions in the North Sea for its challenging results.

On the flip side, Rowan is getting ready to take delivery of three new ultradeepwater vessels by the end of 2015, which should really jack up its growth rate and give it a comparative advantage over older deepwater vessels that aren't as efficient from a production perspective. Because Rowan is smaller than most of its peers -- with just 34 total drilling rigs including what's under production -- it has the potential to grow much faster and control its costs a lot more easily than its foes. That presents an intriguing scenario for investors who are staring down a forward P/E of just seven and a growth rate that could exceed 30% by 2015 when these new vessels are introduced.

Also working in Rowan's favor are the higher day-rates of its ultradeepwater rigs and the high barrier to entry in the contract drilling field. Unless you have billions of dollars to spend, your chances of infiltrating the drilling services market are low, leaving these contractors with plenty of pricing power even if newer rigs are being regularly introduced.

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.