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 Best Buy (NYSE:BBY) slumped another 4% this morning after Goldman Sachs downgraded the electronics retail giant from buy to neutral.

So what: Along with the downgrade, analyst Matthew Fassler lowered his price target to $28 (from $45), representing just 4% worth of upside to yesterday's close. While contrarians might be attracted to yesterday's big 30% tumble, Fassler thinks Best Buy's appreciation prospects remain limited given the strong headwinds still working against it.

Now what: Goldman expects Best Buy to trade in line with secularly challenged retailers once again, after having soared in 2013. "The likely diminished contribution of highly profitable wireless growth and the cycling of Vizio as a key driver of TV share gains impair our confidence as we look forward," noted Fassler. "Management spoke to incremental cost cutting opportunities on its call, but we think the firm will be challenged to deliver superior customer experiences while slashing its cost structure."

Given Best Buy's still-worrisome sales trends and increasingly clear cost disadvantages, it's tough to disagree with Goldman's downgrade.