While Fools should generally take the opinion of Wall Street with a grain of salt, it's not a bad idea to take a closer look at particularly stock-shaking upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Marathon Oil (NYSE:MRO) gained about 1% today after Deutsche Bank upgraded the energy company with a buy rating.

So what: Along with the bullish call, analyst Ryan Todd planted a price target of $46 on the stock, representing about 22% worth of upside to yesterday's close. So while contrarian traders might be turned off by Marathon's year-to-date price strength, Todd's call could reflect a sense on Wall Street that its production growth prospects still aren't fully baked into the valuation.

Now what: According to Deutsche, Marathon's risk/reward trade-off remains rather attractive at this point. "No company has transformed itself as dramatically as MRO, nor has staked its success on US unconventional so explicitly," said Todd. "Since 2010, US unconventional has increased from 3% to 45% of total production and from 6% to 61% of the capital budget (increasing to 45% and 67%, post-Norway). As constructed, we view MRO as an undervalued play on three, high quality onshore basins, offering above average growth, under-appreciated resource depth, and growing cash return/acceleration flexibility on FCF generation post-2014." Given Marathon's 2%-plus dividend yield and industry-lagging P/E of 10, it's tough to disagree with Deutsche's bullishness.