LOS ANGELES (MarketWatch) -- Moody's Investors Service said Wednesday it's reviewing its Baa3 senior debt rating on Humana Inc. (hum) for possible downgrade after the company wasn't awarded a renewal of the Tricare managed care contract covering areas in the South. Moody's review, in part, will focus on the impact the loss of the Tricare contract is expected to have on Humana's financial metrics, operations, and future strategies. The agency said if the Department of Defense, after a possible appeals process, decides to choose different carriers for the Tricare contract, the estimated loss of the contract to Humana would be about $3.5 billion of annual revenue, or 11% of projected total 2009 revenue.