To put it another way, the pitcher’s average quality of contact is more predictive of the quality of contact on a given batted ball than is the batter’s average quality of contact. However, the average quality of contact varies much less among pitchers than it does among batters in major-league baseball. As a result, the identity of the batter is more important in determining the resulting quality of contact than the identity of the pitcher, at least to the extent that we can determine it with these statistical techniques.
– Mike Fast, “Who Controls How Hard the Ball is Hit?”
This piece is cool, but full of all sorts of jargon and it’s a tough read. The basic idea is this: Pitchers have less control over how hard the ball is hit than the batter. Pitchers do have some control, but it’s not as much as the batter, as batters have a wider spread of hitting abilities. I think that passes the intial sniff test — Gary Sheffield hit the ball pretty hard against everyone.