Lydia Ko when she was swinging her best

As some are beginning to notice, Lydia Ko is starting to slump a little bit.  There are some concrete reasons why her game has started on the wrong path.  And it has to do with the changes she has made with her instructor David Leadbetter on her golf swing.  On the right side is her latest swing from 6 months ago.  

  

This is her old setup.  Her left hand grip is a standard strong grip as well as her right hand grip.  Now we can see both her grips are weaker.  This change toward weaker grips is going to straight away promote an open clubface throughout the swing which inevitably will lead to a rolling release (which is bad because it increases the timing required to hit consistently on target shots).  So unfortunately since these great natural talents are unaware of what makes them great, a kind unassuming instructor who has the "credibility" of helping some big name players can talk them into changing to become even better or to gain more distance.

Unfortunately, these changes are just making her more inconsistent and although sure she may be a 5 or even 10 yards longer, if she keeps hitting it offline like she is right now, she will certainly lose that #1 world ranking for good.  Note: Jordan Spieth is on this track too.

     Not much difference here

Look how she is loading into her left side before her backswing is finished.  This is going to lead to less rotation and invite a flip and roll increasing the chances of an inaccurate shot.  This is the difference between Ben Hogan and her.  Ben Hogan had great body rotation and had a great impact with a bowed left wrist and stable clubface through impact.  This is what Lydia had before meeting Leadbetter and it is why she was so consistently great.  But now she is working towards the opposite of those moves that the best ball strikers including Hogan had.  She is losing her body rotation by sliding onto her left leg -- which is affecting the once great impact she had and destabilizing her clubface through impact.

  

Look at how much further left she is nowadays.  And the rotation she once had is almost gone.  Also you can tell that now she has almost no Right Lateral Bend in her spine (look at the green lines -- she used to have the curve in the right side of her body indicating the Right Lateral Bend) which means that her right bicep will likely contract too early leading to the flip and roll because an early right bicep contracting causes the lag to be released.    

From these two pictures you can see that her clubface angle is more open in her new swing.  This means that she will have to time it closed.  And there is just a lot less rotation due to how far she slid to her left side.

Notice how much faster the logo on the golf glove disappears on her worse swing (on the right).  Also notice how her left elbow is rotating away from the target which is also another indication that she has to time a rolling clubface.