I think this clearly lays out the two options that will happen with Matt Cassel.

If the Pats aren’t confident enough in Brady’s knee, and also don’t feel backup Kevin O’Connell can assume a starter’s role, they’ll work out a longer term deal with Cassel. Keeping him for the one-year tender would make no sense, as combined with Brady’s cap figure, that would tie up $29.2 million.

If their concerns about Brady aren’t overwhelming, they’ll use their asset and get the best possible deal. Franchising Cassel on the early side of the two-week window allowed by the NFL may allow more time for a market to develop and a potential deal to materialize. (Source)