I'm late to this topic but I'm in favor of instant replay. It really could work quite well, and similar to football. 1. Each manager gets 1 challenge per game. Challenges can be used on any ball put in play. Challenges can NOT be used on balls and strikes, balk calls, or tag up/sac fly calls. That way the "human element" is retained. (I doubt you'd get the double play challenges because everyone would save that challenge for the really blatant misses.) 2. Challenges cannot be used in the 9th inning or extras. At that point, you have a review ump in the booth that can do "official challenges". As far as the complaint that it will slow down the game, would it really slow it down any more than a Lou Piniella or Bobby Cox tirade currently does? I recognize that baseball is grounded in it's roots, and hates to update the game in any significant fashion, so I doubt that it will happen. But not doing it because it's never been done in the past is silly. Get the calls right. Mistakes are made by umps...they aren't intentional, but calls are missed. No reason not to fix them. If you really want to limit it though, make it on scoring plays only. If the "missed call" happens on a play at the plate, or on a play where a player otherwise may have scored (ex: a homer inadvertantly called a double) than it's reviewable.