Two-time Masters champion Bubba Watson matched the course record with a seven-under-par 63 in Friday's second round of the PGA Championship at Southern Hills.
With nine birdies, the most in any major round of Watson's career, the 43-year-old US left-hander equaled the 18-hole mark set by Ray Flord and matched by Tiger Woods during his run to the 2007 PGA title.
"I'm definitely not going to think about it," Watson said of the historic round. "Because tomorrow whoever I'm playing with is going to be trying to attack the course.
"I could shoot 80-80 and I could care less what I did on Friday."
Watson missed a 23-foot birdie putt at the 18th hole that would have matched him with the all-time lowest round in major golf history, the 62 fired by South African Branden Grace in the third round of the 2017 British Open at Royal Birkdale.
Watson, who won the Masters in 2012 and 2014, smashed drivers all day and missed only one fairway, an aggressive style built from confidence in his power and skill.
"It's about trusting yourself," Watson said. "If you don't trust yourself out there, it doesn't matter if you have the perfect yardage, the perfect club.
"If you don't feel like you can hit a shot or you're second-guessing that shot, then it doesn't matter what golf course it is. It doesn't matter if it's at home with your buddies. You're just trying to trust yourself.
"I trusted it. I was focused on what I had to do, and it worked out."
Watson was helped when brisk early winds died down in the afternoon as he was getting started.
"When that wind died down, you just felt like you had a chance to score," Watson said. "I'm not saying it was easy by any means. I just hit some putts, hit some shots that helped me.
"My whole goal was to make the cut, so I was just trying to stay ahead of the cut line, and every time I made a birdie I just kept saying, that's one more to the good."
He joked to caddie Gabe Sauer at the 12th hole he had to shoot 7-over the rest of the way to make the cut.
"The golf course can get you real fast," Watson said.