Skin Blues wrote:The effect on the pitcher has been looked at before and found to be very minimal.
As a coach I have a different opinion.
It's not only that a baserunner forces the pitcher to an uncomfortable position, but his attention gets divided, and can't focus on the batter 100%.
A speedy baserunner limits the pitcher's repertoire, and locations he can use, which gives the batter a better chance to succeed, since the batter knows that too.
Finally there's an increased stress level, that might not show right there, but contributes to the pitcher's overall mental load, that might only be a factor later in the game.
And the baserunner didn't even moved yet.
To be honest, I never read a study about this, and I'm not aware of the magnitude of the effect, but Im sure that these effects are different at every level, and have different effect on every player as well.
All in all, I have an open mind, so I'd like to read that article, if you'd share that link.