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 Whole Foods Market, (NASDAQ:WFM) plummeted 20% today after the natural-foods grocer posted disappointing Q2 results and received a buy-to-hold downgrade from Deutsche Bank.

So what: Along with the downgrade, analyst Karen Short lowered her price target to $40 (from $60), representing about 17% worth of downside to yesterday's close. So while contrarian traders might be attracted to Whole Foods' big pullback today, Short's call could reflect a sense on Wall Street that its operating headwinds will leave the stock range-bound.

Now what: According to Deutsche, Whole Foods' risk/reward trade-off is rather balanced at this point. "Natural retailers account for 4% of total supermarket units today -- an indication that there is ample room for all of the natural players to take share from conventionals. For now, however, these formats are growing at ~15% -- well above conversion rates at the consumer level," said Short. "This disconnect is leading to excess capacity in the near term -- or 'temporary saturation', and until this situation shakes out through consolidation, store closures and market exits, all participants in the space may feel some pain." With Whole Foods shares now off about 40% from their 52-week highs, however, those short-term concerns might be providing patient Fools with a solid long-term entry point. 

John Mackey, co-CEO of Whole Foods Market, is a member of The Motley Fool's board of directors. Brian Pacampara has no position in any stocks mentioned. The Motley Fool recommends and owns shares of Whole Foods Market. 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.