Matt Cassel is a fourth year player out of USC. He has backed up QB's such as Matt Leinart, Carson Palmer, and of course Tom Brady.
In the press conference yesterday, Belichick turned down all accounts of having Tim Rattay and Chris Simms come for a practice session/tryout. From sources I have I was told both Rattay and Simms arrived in Foxborough yesterday, and both were told to go back home by Patriots GM of Operations because the organization was no longer interested.
By this time almost everyone in the world knows that Brady is out, but you have to remember that Tom Brady was built on a situation just like this one. You can recall an injured Drew Bledsoe and the emergence of a future two-time Super Bowl MVP.
Give Matt Cassel time to develop. Remember, Brady didn't go 16-0 in his first season.