What do you think is the most important aspect of the swing that is not commonly emphasized? The 3 imperatives are not eligible for nomination.
I think footwork and dynamic balance (I think they go hand-in-hand) are often overlooked. I don't think there is any reason for a player not to have excellent, professional quality footwork in their swing. It's easy, just a matter of practice.
Two of the best as far as footwork go in my opinion are Mac O'Grady (look at historicgolf.com) and Steve Elkington.
By the way, if your heel doesn't lead your toes (face-on view) in the first part of the downswing, you probably don't have professional quality footwork. If you are off your heel during the transition of your swing, again, you probably have some room for improvement.
I found out I had an ankle mobility issue that led to coming off my right heel almost immediately. Solution? Practice rolling onto the inside of the right foot, just as Nicklaus did with Jack Grout, hitting balls while not coming off the right heel.
Matt
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"In my experience, if you stay with the essentials you WILL build a repeatable swing undoubtedly. If you can master the Imperatives you have a champion" (Vikram).
The reason you can't sustain the lag is because you are so eager to make the club move fast (a reaction to the intent of "hitting it far"). So on a full shot you throw it away too early, which doesn't happen for your short chip. (bts)