The massive debt load carried by Sam Zell-owned Tribune guarantees a paper-thin margin for error in its operations. Credit analyst David Novosel estimates that the company has $4 billion in debt and interest payments to make in 2009, practically requiring major asset sales, reports Reuters. This is the context behind the planned sale of the Chicago Cubs, as well as Long Island paper Newsday.

So how close is Tribune to actually defaulting? The company’s debt covenants require it to maintain a debt-to-trailing-EBITDA ratio of 9-to1, a ratio that will narrow to 8.75-to-1 in 2009. According to Fitch, the company was at 8-to-1 at the end of 2007, meaning there’s very little wiggle room.

The Reuters (NSDQ: RTRSY) piece also looks at what else Tribune could offload if it needs to rustle up cash. It holds a 31 percent stake in the food network, as well as other broadcast operations. But eventually you’re just talking about gutting the core business, which undermines any effort based on a turnaround.