Joe Crede .260/.336/.480 is an All-Star.
Jason Friggin Varitek .219/.301/.360 is an All-Star.
Carlos Quentin .273/.378/.513 is an All-Star.
Jason Giambi .259/.395/.543 is not an All-Star.
Neither is Jorge Posada .281/.361/.446.
Making the case for Mike Mussina is harder. The starters who beat him have better numbers. Do you really need six relievers on the team? I'm not sure if there are rules for how many starters/relievers the team can carry. I'm also not sure if Francona could have taken Mussina over, say, Varitek or Crede.
I know that several of the starters will be unavailable because they'll start the last day of the first half, that guys will be replaced because they're sore or injured.
But you really mean to tell me that there was no room on the team for Mike Mussina?