Quick answer: Face-on: the wrist-shaft angle opens as soon as the downswing starts; with the lead arm horizontal, the angle to the shaft already exceeds 120 degrees.
What it does to the ball
No lag: a big loss of distance, a high weak flight, and fat strikes because the low point moves back.
Root causes (by frequency)
Trying to create speed from the top with the hands
A reversed sequence: arms before hips
A grip so tight it locks the wrists
How to fix it
Hold the wrist angle until your hands pass the trail thigh: speed is released at the bottom, not from the top
Drills that fix it
Lag pump · 15 min · 12 reps
Hold the wrist angle on the downswing From the top, swing down slowly until your hands reach the trail thigh, keeping the angle between the lead arm and the shaft; swing back up and repeat twice. On the third pump, hit the ball. The feeling is of holding back, not of force.
Drag the towel · 10 min · 15 reps
Feel the hands leading and the clubhead arriving late Tie a small towel to the head of an old iron and make swings feeling the towel always trailing behind the hands. Then hit low punch shots with a real ball, keeping that dragging feel.
Frequently asked questions
What is "Casting (early loss of lag)" in the golf swing?
Face-on: the wrist-shaft angle opens as soon as the downswing starts; with the lead arm horizontal, the angle to the shaft already exceeds 120 degrees.
What does casting (early loss of lag) do to the ball?
No lag: a big loss of distance, a high weak flight, and fat strikes because the low point moves back.
How do you fix casting (early loss of lag)?
Hold the wrist angle until your hands pass the trail thigh: speed is released at the bottom, not from the top