Couple of things: It's insane to do something like this without giving guys like Steven, Parker or Gaub a chance (as TT mentioned). Secondly, there's more to consider than Z's chances of success and value out of the pen. Even if you assume Z might not be that much less valuable as a high-leverage reliever, it's still going to weaken the starting rotation if you are essentially substituting Gorzelanny or Silva (however you want to look at it) for Zambrano as a starter every fifth day. I'm a actually a big fan of Gorzelanny, but he's extremely unlikely to be as good as Zambrano as a starter. Silva's career numbers speak for themselves. It's great that he's been so good early on, but it's (to use this phrase one more time) extemely unlikely to continue anywhere close to that level. Looking at their careers, Silva can't even carry Zambrano's jock strap. Is it possible this could work out? Yeah, I guess. But you aren't playing the percentages. It's far more likely to bomb.