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 McDonald's Corporation (NYSE:MCD) slipped 1% on Wednesday after Wells Fargo downgraded the fast-food giant from outperform to market perform.

So what: Along with the downgrade, analyst Jeff Farmer maintained his valuation range of $100 to $102, representing about 5% worth of downside to yesterday's close. While value investors might be attracted to the stock's sluggish action during the past several months, Farmer believes that top-line headwinds should continue to limit multiple expansion going forward.

Now what: Wells expects McDonald's ROIC to continue to slip in 2014. "McDonald's U.S. market share losses in three of the last four months through November have increasingly captured our attention," noted Wells. "MCD was more aggressive in 2013 with both new products and promoting value, but the company's recent U.S. market share losses suggest that the long-delayed raising of the competitive bar by [Wendy's] and [Burger King Worldwide] is creating a tangible top-line headwind for McDonald's, and one we expect to persist in 2014." With McDonald's shares currently boasting a 3%-plus dividend yield, however, those short-term concerns might be providing patient Fools with a solid long-term income opportunity.