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 Cisco Systems (NASDAQ:CSCO) slipped 1% this morning after JPMorgan Chase downgraded the networking gear gorilla from neutral to underweight.

So what: Along with the downgrade, analyst Rod Hall lowered his price target to $17, representing about 23% worth of downside to Friday's close. While contrarians might be attracted Cisco's decline over the past six months, Hall believes there's more room to fall given the emerging market headwinds -- slowing demand, depreciating currencies, and declining GDP estimates -- continuing to work against the company.

Now what: According to JPMorgan, Cisco's risk/reward trade-off is particularly unattractive at this point. "Carrier revenue trends in major emerging markets look likely to weaken further in 2014," noted Hall. "We believe that these negative revenue trends combined with weak local currencies are likely to drive lower capital spending." With the stock now off more than 15% from its 52-week highs and trading at a 3%-plus dividend yield, however, those short-term concerns might provide patient Fools with a juicy long-term income opportunity.