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 Markwest Energy Partners, L.P. (UNKNOWN:MWE.DL) slumped about 3% this morning after Wunderlich Securities downgraded natural gas transporter from buy to hold.

So what: Along with the downgrade, analyst David Askew lowered his price target to $68 (from $78), representing about 7% worth of upside to yesterday's close. While Askew remains bullish on Markwest's long-term prospects, he thinks that elevated funding needs will continue to limit distribution growth over the next several months.

Now what: According to Wunderlich, Markwest's short-term risk/reward trade-off isn't too attractive. "[W]e believe investors are concerned over the return profile on the CapEx and the lead time required to achieving the stated mid-double-digit ROIC targets, which we believe will limit near-term valuation expansion," noted Askew. "Although MWE will likely be capable of double-digit distribution growth from 2016-2018 and potentially beyond, we believe the risk profile has increased and investor fatigue will keep units range bound in the next 6-9 months." With the stock off about 15% from its 52-week highs and currently boasting a 5%-plus dividend yield, however, those short-term concerns might be providing patient Fools with a juicy long-term income opportunity.

Brian Pacampara has no position in any stocks mentioned, and neither does The Motley Fool. 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.