The Mosaic Company (MOS) is slated to take its turn on the earnings stage after Monday's closing bell, with the agricultural chemical concern set to unveil its fiscal first-quarter results.

Analysts surveyed by Thomson Reuters are anticipating a profit of 72 cents per share, substantially higher than the company's year-ago earnings of 23 cents per share. Mosaic has a dismal history in the earnings spotlight, having fallen short of Wall Street's consensus profit expectations in three of the past four quarters.

I was scanning through stocks that made substantial pre-market moves to bring to your attention and I found just that in Micron Technology (MU).

The tech firm was more than 3% lower before the bell thanks to a downgrade from Goldman Sachs. The brokerage cut MU to neutral from buy. Goldman noted that it "underestimated the impact tablets would have on the PC supply chain, with tablets cannibalizing notebooks faster and to a greater degree than we [the brokerage] had expected." Goldman Sachs also stated that MU was negatively impacted by Inotera's delay of its 50mm transition.

Chesapeake Energy (CHK) Monday morning was upgraded to outperform from market perform at BMO Capital. The brokerage house cited valuation as the reason for the upgrade, stating that the shares are "attractively priced at three times next year's expected discretionary cash flow compared to a median multiple of around five times at the group's larger peers," according to MarketWatch.

BMO also feels CHK's use of joint ventures to raise cash and finance capital expenditure could lead to higher cash flow yields and returns on capital, MarketWatch reported. Along with the upgrade, the ratings house assigned a price target of $30 per share for CHK.

Friday morning, UBS issued an upgrade to Costco Wholesale (COST), elevating the warehouse retailer to buy from neutral.

The upgrade was made based on valuation, as UBS feels that recent weakness in the stock price offers a good entry point. In fact, UBS notes that Costco has "one of the world's best retail business models." The brokerage noted that removing calendar shifts and gas sales from Costco's comparable sales figures shows an "improving trend in all categories and in all U.S. regions."

Solar provider LDK Solar (LDK) rallied a bit in pre-open and early trading thanks to an upgrade from Bank of America/Merrill Lynch. The brokerage elevated LDK to buy from underperform, which is a two-level upgrade. The ratings house based its upgrade on the fact that it sees lower risks of oversupply.

Technically, LDK may need a bit more than this rally to help it finally break through overhead resistance. The stock is trading in the $6 region thanks to the upgrade, but it needs far more momentum. The shares face double-barreled resistance from their 10- and 20-week moving averages. These trendlines are descending through the upper reaches of the $6 region, and are quickly falling toward LDK's current position.

Analyst upgrades

• Deutsche Bank upgraded Sonoco Products (SON) to buy from hold after the company reported Q1 results and raised guidance. The firm upped its target for shares to $38 from $32.
• Baird upgraded Western Digital (WDC) to outperform from neutral following the solid Q3 report and guidance. The firm raised its target to $50 from $48.
• Goldman upgraded Qwest (Q) to neutral from sell. Qwest is being acquired by CenturyLink (CTL).
• Hershey (HSY) was upgraded to neutral from underweight at JPMorgan.
• Principal Financial (PFG) was upgraded to neutral from sell at UBS.
• Monster Worldwide (MWW) was upgraded to market perform from underperform at Wells Fargo.

Tuesday morning, Tudor Pickering Holt decided to upgrade Devon Energy (DVN) to accumulate, noting that the company is a "cash-rich company with solid-but not-outstanding assets that trades at a discount." The brokerage house believes that Devon will issue a $3 billion share buyback program, leading to the upgrade.

The company is the largest producer and largest lease holder in the Barnett Shale area of North Texas, and has exploration and production assets in North Texas, Oklahoma, Wyoming, and western Canada. The company's impressive success rate and substantial assets suggest that the company will continue to perform well.

Starbucks (SBUX) is set to have a good morning, as the company received an upgrade from UBS to buy from neutral. The brokerage also upped its earnings forecast for Starbucks to $1.14 per share in fiscal 2010, up from $1.09 per share. For 2011, UBS expects Starbucks to pull in $1.34 per share, seven cents better than the brokerage's earlier forecast. UBS believes that benign costs and Starbucks' ongoing productivity programs are key to the company's success. That said, UBS feels that McDonald's (MCD) foray into the world of frappes and smoothies could "cannibalize frappuccino consumers from Starbucks." Such a move could hurt Starbucks' bottom line.