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

What: Shares of Freeport-McMoRan Copper & Gold (NYSE:FCX) slipped 2% this morning after Goldman Sachs downgraded the mining giant from buy to neutral.

So what: Along with the downgrade, analyst Sal Tharani planted a price target of $37 (from $36) on the stock, representing about 3% worth of upside to yesterday's close. While contrarians might be attracted to Freeport's share-price surge since late June, Tharani believes the company's near-term prospects are now baked into the valuation.

Now what: Goldman thinks Freeport's risk/reward trade-off is pretty balanced at this point. "We downgrade FCX to Neutral from Buy, as the stock trades near our price target and we do not see any near-term catalysts to drive the stock," Goldman noted. "While we remain positive on its long-term outlook on the back of its organic growth projects in copper and oil, we view these benefits as priced in." With the stock still trading at a clear price-to-cash flow discount to the industry and boasting a 3.5% dividend yield, however, those short-term concerns might provide patient Fools with a juicy long-term income opportunity.