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 Align Technology (NASDAQ:ALGN) sank 4% today after Baird Equity Research downgraded the purveyor of invisible braces from "outperform" to "neutral."

So what: Along with the downgrade, analyst Jeff Johnson reiterated his $49 price target on the stock, representing just 2% worth of upside to yesterday's close. While Johnson remains bullish on Align's earnings prospects, he believes that the stock's steady run-up in 2013 leaves investors with little upside to work with.

Now what: Baird still expects solid near-term growth out of Align.

"Downgrading ALGN to Neutral is not meant to be a call on the company's 3Q, especially as our intra-quarter checks have been generally positive and we still expect modest upside to our/Street's projections this quarter," noted Baird. "Further, we continue to like that management has seemingly gone on the offensive recently in both the high- (G4/SmartTrack) and low-acuity (Express 5/Realine) segments of orthodontics."

With the stock up about 65% in 2013 and trading at a forward P/E of 30, however, I'd agree with Baird's assessment that those prospects are already baked into the valuation.