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 analyst upgrades and downgrades -- just in case their reasoning behind the call makes sense.

What: Shares of Kellogg (NYSE:K) slipped 2% in premarket trading Tuesday after Goldman Sachs downgraded the cereal giant from neutral to sell.

So what: Along with the downgrade, analyst Jason English lowered his price target to $59 (from $64), representing about 11% worth of downside to yesterday's close. So while contrarians might be attracted to Kellogg's price weakness since early June, English's call could reflect a sense on Wall Street that its growth prospects are just too limited to trigger a significant rebound.

Now what: Goldman lowered its 2014, 2015, and 2016 EPS estimates by 4%, 6%, and 6%, respectively. "[T]op-line rejuvenation efforts are falling flat and the portfolio is coming under what we believe is a retail lead SKU rationalization knife," said English. When you couple that downbeat view with Kellogg's hefty debt load and forward P/E of 15, it's tough to disagree with Goldman's bearish stance. 

Brian Pacampara has no position in any stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. 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.