There s nothing like a good bullpen. Look at the Mets and the Giants. Both have great bullpens and mediocre starting staffs. But their relievers regularly save the starters bacon. This means Dusty Baker and Bobby Valentine leave the starters in longer and the starters get wins they wouldn't otherwise deserve.
New pitchers have an advantage.
Sometimes it takes a while for teams to figure a pitcher out. Until they do, that pitcher will consistently get them out. Detroit s Dave Mlicki comes to mind. In the National League he was an underachiever with good stuff. This year his ERA was 2.79 after six starts.