Hank Haney, former coach to Tiger Woods, has raised questions over Bernhard Langer's putting technique.
The 59-year-old recently made it back-to-back senior major wins at the Senior PGA Championship to complete the grand slam - but question marks are continuing to hang over his putting method, which Haney believes is very close to, if not, anchoring.
The coach took to Twitter to call out the USGA and demand an explanation on Langer's technique, before adding that a lot of the German's peers on the Champions Tour are beginning to question it, too.
Golf Channel analyst Brandel Chamblee also weighed in with his thoughts.
This is what nonanchoring is meant to look like. If I wanted to putt with a long putter and remove all doubt, I'd follow suit pic.twitter.com/5ltItb0zuo— Brandel Chamblee (@chambleebrandel) May 31, 2017
Honestly I thought that's what it was supposed to look like too. I guess I was mistaken. https://t.co/42dpvgEUZy— Hank Haney (@HankHaney) June 1, 2017
The anchoring ban came into force on January 1, 2016, after the R&A and USGA became worried that players were turning to long putters as an advantage instead of a last resort.
To anchor the club is defined by players intentionally holding the club or the hand gripping the club in contact with any part of the body.
In outlining the reasons behind the ban, USGA executive director Mike Davis said: "Throughout the 600-year history of golf, the essence of playing the game has been to grip the club with the hands and swing it freely at the ball.
"The player's challenge is to control the movement of the entire club in striking the ball, and anchoring the club alters the nature of that challenge.''