MAYBE STACK AND TILT IS BETTER FOR HIS KNEES.
ATLEAST GIVE HIM TIME TO GET USED TO IT.
The poor weekend at the U.S Open can be attributed to short game issues. His ball striking, despite some missclubs here and there, was exceptional throughout Memorial and the U.S Open.
Trust me it's not a dependable swing, not a go-to swing, like he had before. Way too controlled, contrived, forced, and unnatural...his body is fighting it. He needs to get back-to-basics; most notably his alignment, natural weight transfer, better footwork, extension and release. I've been studying the golf swing for over 25 years, and his since he won the U.S. Amateur three times.