At a recent game, I was PU, 16 year olds, home team pitcher has a rep as being a very emotional player, aggresive player, but I've never seen him do anything dirty in the many games I've seen him.
He's warming up in between innings and the on-deck batter is not in the on-deck circle area, I'd say was standing maybe 10ft away from the plate watching the pitches come in working out his timing. I turn for a second to glance in the dugout, and I hear the on deck batter get plunked with a warm up pitch in the shoulder. Long story short pitcher says it slipped, I warned him, (and warned the batter to stay in the on-deck circle next time) batter was fine, and on the game went. In my mind I thought there's no way a pitch can get that far "away" from him, and he did have a reputation, and he never said much to the on deck batter for hitting him.
I don't usually let on deck batters stray too far out of the on deck circle during warm ups, but in this case I said nothing. Now I've heard some pitchers don't want on-deck batters anywhere near the plate when they're warming up, in fact I've heard it to cause bench clearing brawls.
How strictly do you enforce the on deck batter staying in the circle during warmups?