He was three-over-par through nine holes before being informed at the 10th tee of his violation of rule 4.1a, for using a non-conforming club.

Chief referee Steve Rintoul said a substance that looked like white paint had been applied to the surface of one of Matsuyama's clubs.

"Those markings were placed there by his club guy to help with alignment," Rintoul said.

"Assistance with alignment by placing a small Sharpie mark on the face ... is certainly allowed, but what was done there with that substance, which is very much like a White-Out substance we would use at home, was a coating that was not only in the grooves, but was very thick along the face ... which renders the club non-conforming."

Matsuyama admitted using the club on the 1st tee, Rintoul said.

Rintoul added someone in the golf industry whom he declined to identify pointed out pictures of Matsuyama's club that had been taken a few days ago.

They reached Matsuyama too late to keep him from using the club in competition.

"The damage was done on the 1st hole," Rintoul said. "Just unfortunate set of circumstances for Hideki, for sure."

Matsuyama, 30, won the first of his eight PGA Tour titles at the Memorial in 2014.

At the 2021 Masters, he became the first Japanese golfer to win a men's major championship.

He is currently ranked No.12 in the official world rankings.