Like most closers, Rivera didn't have the sustained stuff to be a starter. It's probably somewhat true he's gotten by all these years with one pitch, his cut fastball. But he has poise to rattle anyone else. Closers who are more than flashes in the pan usually bounce around to several teams, losing and regaining their mojo unpredictably. Mariano has been the foundation of the Yankees bullpen for eighteen years.
I've actually wanted him to retire for a few seasons now, not wanting to see his performance dip. He spent most of last season injured, which helped me prepare for today's announcement. It will still feel odd to realize he's truly retired. The Yankees may have to wait a few generations for another closer of his caliber.
You wanna know who the best is? That's him: Iceman. It's the way he flies, ice cold. No mistakes. He just wears you down. You get bored, frustrated, do something stupid, and he's got you.