What it is
People call it pulling off the ball. Coach Bass looks at where the momentum of the body goes instead. The front shoulder should be attacking the ball: when the hitter starts the swing, the front shoulder goes toward the ball. Right-handed hitter: momentum goes toward the second baseman. Left-handed hitter: momentum goes toward the shortstop.
Why it matters
The ball is in front of the hitter at all three attack points: the inside front knee, the belly button and the inside back knee. The hitter needs the correct momentum direction to get behind the ball. "Pulling off" is only the description people use; the correction is about where the hitter's momentum goes.
What to look for
The front shoulder is the tell. Watch whether it attacks the ball or pulls away. Know which side the hitter bats from before you judge it: the direction is the second baseman for a right-handed hitter and the shortstop for a left-handed hitter.
How to do it
Take your momentum toward the second baseman (right-handed hitter) or the shortstop (left-handed hitter) and take his or her cap off with a line drive. That one thought is the whole correction, and it stays that simple. The Middle-Away Line Drive drill trains the same direction.
What good looks like
Line drives toward the middle of the field, through the second baseman for a righty and the shortstop for a lefty, instead of pulled-off contact. The front shoulder goes toward the ball when the swing starts.