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 Safe Bulkers (NYSE:SB) gained 2% yesterday after Jefferies upgraded the dry bulk transportation company from hold to buy.

So what: Along with the upgrade, analyst Douglas Mavrinac planted a price target of $11 on the stock, representing about 26% worth of upside to Thursday's close. So while momentum traders might be attracted to Safe Bulkers' sharp pullback since early March, Mavrinac's call could reflect a growing sense on Wall Street that the company's prospects are becoming too cheap to pass up.

Now what: According to Jefferies, Safe Bulkers' longer-term risk to reward trade-off is rather attractive. "While we are also reducing our 2Q14 estimates to reflect the weak start to the quarter, we continue to believe the outlook for 2H14 & 2015 is very attractive given the significant new iron ore production capacity being brought online in Australia and Brazil," said Mavrinac. "Given the attractive outlook, we are upgrading SB shares to Buy from Hold." When you couple that upbeat outlook with Safe Bulkers' cheapish forward P/E of eight, it's tough to disagree with Jefferies' upgrade.