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 National-Oilwell Varco (NYSE:NOV) slipped slightly in pre-market trading Monday after Goldman Sachs downgraded the oil-field services giant from buy to neutral.

So what: Along with downgrade, analyst Waqar Syed lowered his price target to $85 (from $90), representing about 13% worth of upside to Friday's close. So while contrarians might be attracted to the stock's year-to-date slump, Syed's call suggests strengthening bearishness on Wall Street over its near-term turnaround prospects. 

Now what: According to Goldman, National-Oilwell's risk/reward trade-off is pretty balanced at this point. "As competition increases between new rigs entering the market and older rigs coming due for re-contracting, we see dayrates declining and hence lowering the incentive for companies to order new rigs at this point," noted Syed. "NOV has a high degree of leverage to this newbuilding cycle, and we prefer to stay on the sidelines as inbound orders will likely slowdown in 2014, and book-to-bill falls below 1.0 in 2H 2014." Of course, with the stock off about 12% from its 52-week highs and sporting a cheapish forward P/E of 11, those short-term concerns might be giving energy-savvy Fools with a solid long-term opportunity.

Brian Pacampara has no position in any stocks mentioned. The Motley Fool recommends National Oilwell Varco. The Motley Fool owns shares of National Oilwell Varco. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.