J.J. starts it back with his arms to prevent an early move to the inside. At hip high, the clubhead is in line with his hands. Perfect.
Staying Sync
After starting back with the arms, J.J. adds body turn. This keeps the swing in the correct sequence. His hands are right in the middle of his chest in this position, a good checkpoint for any golfer.
Watch the Gap
One of the great positions in this swing is the gap between J.J.'s arms and head at the top. You could throw a softball through that gap; with the irons, make it a football. This space proves that his arms and body have completed the backswing at the same time. If his arms kept swinging after his body stopped turning, that gap would close, and J.J.'s swing would lose its great sequence and rhythm.
Feet Stay Quiet
A lot of players are way up on their right toes at impact. Here the right heel is just starting up, proving that J.J. has created a solid base to turn over. Same goes for his left foot going back.
No Flipping
The clubhead is well behind a line drawn from his chin through his hands. He's not flipping the club so the face stays very stable.