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 ENSCO (VAL) slipped slightly today after Jefferies downgraded the offshore contract driller from buy to hold.

So what: Along with the downgrade, analyst Brad Handler planted a price target of $56 on the stock, representing about 12% worth of upside to Friday's close. So while contrarian traders might be attracted to ENSCO's sharp price decline over the past year, Handler's call could reflect a sense on Wall Street that its troubles still aren't fully baked into the valuation.

Now what: According to Jefferies, ENSCO's risk/reward trade-off is pretty balanced at this point. "With (still) >1/3 of its revenues after newbuild deliveries derived from jackups, including markets that could see pressure 'first', such as Mexico, the GoM and SE Asia, we lower EPS and in turn our Price Target (to $56) for ESV, no longer supporting our Buy-rating," said Handler. With ENSCO shares flirting with their 52-week lows and currently boasting a 6% dividend yield, however, those short-term concerns might be providing patient Fools with a juicy long-term income opportunity.