Quick answer: Face-on: the ball sits behind the middle of the stance with mid irons; the shaft leans excessively toward the target at address.
What it does to the ball
Very low flight pushed to the right: the club arrives on an in-to-out path with very little dynamic loft.
Root causes (by frequency)
Moving the ball back in search of clean contact
Fear of hitting it fat
How to fix it
Reposition: wedges dead center and mid irons one fist forward, with an alignment stick between your feet as a reference
Drills that fix it
Dead center · 10 min · 12 reps
Fix the ball-back position and recover dynamic loft Mark the center of your stance with a stick between your feet. Place the ball exactly there with wedges, and one fist forward with mid irons. Hit three-quarter shots, checking that the flight regains height.
Frequently asked questions
What is "Ball position too far back" in the golf swing?
Face-on: the ball sits behind the middle of the stance with mid irons; the shaft leans excessively toward the target at address.
What does ball position too far back do to the ball?
Very low flight pushed to the right: the club arrives on an in-to-out path with very little dynamic loft.
How do you fix ball position too far back?
Reposition: wedges dead center and mid irons one fist forward, with an alignment stick between your feet as a reference
Sources
David Leadbetter — The Golf Swing
PGA of America — PGA Teaching Manual: The Art and Science of Golf Instruction