[Strangler Lewis]

I don't see how a sport that still allows double plays to be turned by middle infielders in the vicinity of second base can introduce instant reply. Plus, as Alex has alluded to, unlike with football or tennis, there are things that can be happening with other base runners that can be affected by the blown call. It sounds like a big headache to puzzle out the situations in which it could be used from the situations in which it couldn't.

I would hate to see instant reply used on balls and strikes. Unlike with football or tennis, the authority of the umpire is a big part of the culture. However, if it turns out that balls and strikes can be challenged, the umpires have only themselves to blame with guys like Eric Gregg saying, "Hey, you know what my strike zone is."