Is an on-deck batter required?

[tommyleo]

The Marlins had a walk-off no-hitter today. Crazy stuff. See here.

The Marlins' winning pitcher was actually on-deck when this happened. But considering the situation -- two out, bases loaded, bottom 9th, tie score -- he had absolutely no chance of batting in that inning. Yet there he was in the on-deck circle, swinging a weighted bat and wearing a helmet.

Discussing this with a friend tonight, he said that the next batter due up is required to be in the on-deck circle. When I asked him to cite the rule, he said that he had heard announcers talk about this requirement over the years. I reminded my friend that announcers sometimes get the rules wrong.

I could not find a rule mandating Major League hitters to be in the on-deck circle when due up next. Am I missing something?