Cassel had been the backup in New England when Tom Brady, a two-time Super Bowl MVP, was injured minutes into last season's opener. Cassel hadn't started a game since high school but helped lead the Patriots to an 11-5 record. It wasn't, however, good enough for a playoff berth.
Brady has suffered setbacks in his return from a torn ligaments in his knee, including a second operation to fight an infection. The Patriots tagged Cassel as their franchise player, meaning they would have to pay him $14.5 million to keep him on the roster as insurance.