When was the last time Prior was good even when he was healthy enough to walk to the mound? My personal view is that he is doner than done. Like even worse that Carl Pavano Done (and that's pretty done!). In terms of risk, Prior is not just as injury-prone as Wile E. Coyote but he also hasn't shown diddly in years. If you're gonna gamble on risky SP, I'd much rather gamble on guys who at least have continued to show good stuff when healthy (RJ, Pedro, Sheets, Harden, etc.).
I am the Master. Don't question the Master. Just do what he says and be proud.