There's probably an obvious answer I'm not thinking about....but with no one on base, no need to frame/receive the ball, and no umpire to protect, is there a rule that requires someone to catch/attempt to catch the pitch? Or can they go be a ninth fielder? I remember something about number of players starting in fair territory, but even like 40 feet back to catch foul tips/foul pop ups seems more 'effective' defensively. I would hate to be the pitcher who pitches to a catcher forty feet back of home.