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 AutoZone (NYSE:AZO) gained about 2% today after Stifel upgraded the auto replacement parts retailer from hold to buy.

So what: Along with the upgrade, analyst David Schick planted a price target of $570 on the stock, representing about 8% worth of upside to yesterday's close. So while contrarian traders might be turned off by AutoZone's price strength over the past year, Schick's call could reflect a sense on Wall Street that its recent operating momentum gives the stock some solid room to run.

Now what: After meeting with AutoZone's management, Stifel is rather bullish about AutoZone's near-term risk/reward trade-off. "AZO experienced stronger trends in the Northeast and Midwest last Q driven by colder winter weather and easier compares y/y," said Schick. "The West Coast underperformed relative to strength in these regions (not as much upside from weather). Management remains optimistic about a continuation of parts breakage with hot summer weather." When you couple AutoZone's still-hefty debt load with its near-20 P/E, however, I'd hold out for a wider margin of safety before buying into that bullishness. 

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.