Hours after Webb Simpson matched the course record at Oak Hill's East Course, Jason Dufner went one lower to set a new record at the famed venue.
Dufner got off to a quick start as he holed out for eagle on the par-4 second. He carded five birdies and 12 pars the rest of his round for a 7-under 63, which set a new course record.
Simpson had posted a 64 earlier in the day to match the old record that Ben Hogan set in 1942 and Curtis Strange matched in 1989.
Dufner's bogey-free gem wiped those three from the record book. Following his eagle on the second, Dufner converted back-to-back birdie efforts at four and five to move to 6-under.
The two-time winner last season on the PGA Tour then parred five in a row. Dufner dropped his tee shot inside six feet at the 11th, and converted that to join Adam Scott atop the leaderboard at minus-7.
At the par-5 13th, Dufner rolled in a 7-footer for birdie to grab the lead by himself. He sank a 5-foot birdie effort at 16 to get to 9-under.
Dufner had birdie chances at 17 and 18, from 22 and 12 feet respectively, but failed to convert either. If one of those putts had dropped, Dufner would have been the first player in history to shoot 62 in a major. Instead, he is the 24th to post a 63.
"It's tough. Obviously, I show a bit of nerves there leaving it short. That's one you'd like to gun at and give a chance at history, but I was able to get the 2-putt and share a little bit of history, I guess," Dufner said when asked if he was nervous over his putt for 62.