Former champion Hideki Matsuyama was disqualified from the Memorial in Dublin, Ohio, midway through his first round on Thursday due to an illegal marking on one of his clubs.
Matsuyama, who earned the first of his eight PGA Tour wins at the 2014 Memorial, was disqualified from the Jack Nicklaus-hosted event after painted lines were discovered on the face of his three wood.
It marked the first time the former Masters champion has been disqualified from a PGA Tour event.
PGA Tour Senior Tournament Director Steve Rintoul said images of the club were posted online and his team only learned of them after Matsuyama used it on the first tee. Had he not used the club, he could have kept playing.
Rintoul said his team approached Matsuyama on the second hole to ask if he had used the club and the former Masters champion was forthright about it.
"The material was applied to the face for alignment for Hideki to set the ball inside the circle of the lines. That's actually the center of the face," Rintoul told reporters.
"And applying a small, discrete dot with a Sharpie to help you with alignment is fine. We have players who do it all the time. But the amount of substance that was up on the face of the club, when we sent it to the USGA, their equipment standards guys, it was just excessive.
"And that's what could affect — could affect — the performance of the ball."
Matsuyama, playing in a group alongside Rory McIlroy and Patrick Reed, was three-over-par 39 when he reached the turn at Muirfield Village after a double-bogey at the second hole and bogey at the sixth.