I had the exact same thought when I heard Perez was starting. It's Game 7, you may as well throw everyone out there. You also have the advantage of no one getting very tired. Of course, that didn't seem to matter with Trachsel in Game 3, but whatever.
Al, did you see Rob Neyer's article today about how Perez is the worst starting pitcher for a Game 7 in history? Suppan was right at the bottom of the list as well.