Analyst upgrades:

• FBR Capital upgraded AutoZone (NYSE: AZO) to Market Perform from Underperform on valuation following the company's Q4 results but lowered its target on shares to $134 from $137.
• Citigroup upgraded Calpine (NYSE: CPN) to Buy from Hold on valuation following Wednesday's sell-off. The firm believes Harbinger's share sale reflects an issue with the shareholders, not with the company, and raised its price target on the stock to $16.50 from $13.
• Credit Suisse upgraded Knight Transportation (NYSE: KNX) to Neutral from Underperform and raised its target to $17 from $16 based on valuation and the improved freight environment.
• Citrix Systems (NASDAQ: CTXS) was upgraded to Conviction Buy from Buy at Goldman.
• Webster Financial (NYSE: WBS) was upgraded to Outperform from Sector Perform at RBC Capital.
• Dr. Reddy's Labs (NYSE: RDY) was upgraded to Overweight from Equal Weight at Morgan Stanley.

MAJOR PAPERS:

• The Wall Street Journal reported that KKR Financial Holdings LLC (NYSE: KFN), a unit of Kohlberg Kravis Roberts, revived concerns of a credit crunch after it asked for a restructuring of billions of dollars in short-term debt.

• According to sources, the Chicago Tribune reported that Deutsche Lufthansa AG (OTC: DLAKY) could look to take an equity stake in a merger between Continental Airlines Inc (NYSE: CAL) and UAL Corporation's (NASDAQ: UAUA) United Airlines.
• The Associated Press reported that the pilots' unions of Delta Air Lines Inc (NYSE: DAL) and Northwest Airlines Corporation (NYSE: NWA) are unable to agree on how seniority for the companies' pilots would work under a combined carrier. The impasse puts the deal in "serious jeopardy," inside sources reported.

• Electronics retailer Sharper Image Corporation (NASDAQ: SHRP) has filed for bankruptcy, citing declining sales and profitability, Bloomberg reported.