Americans Jimmy Walker and Robert Streb shared the lead heading into the third round of the US PGA Championship after record-equalling performances at Baltusrol.
Walker added a 66 to his opening 65 to post a nine-under-par score of 131 and equal the lowest halfway total in the year's final major, although he bogeyed the last to cost himself a share of the all-time major record of 130 held by Martin Kaymer, Brandt Snedeker and Nick Faldo.
The 37-year-old was then joined at the top of the leaderboard by unheralded compatriot Streb, who carded eight birdies and a solitary bogey to become the 28th player to shoot 63 in a major.
Defending champion Jason Day and Argentina's Emiliano Grillo were two shots behind after rounds of 65 and 67 respectively, Day recovering from a double bogey on the seventh to birdie seven of the next eight holes.
And Open champion Henrik Stenson was just a shot further back in his bid to win two major titles in the space of three weeks after carding a second consecutive 67.
Walker was unaware of the record possibilities as he stood on the 18th tee and promptly drove into the water to the left of the fairway and compounded the error by three-putting from long range.
"The finish wasn't what I was looking for - but it's fine," the five-time PGA Tour winner said. "I think you take 66 at any tournament all day every day.
"So it's good. It's really cool. You're at the PGA Championship. You are at the top. It's what you are here to do. It's fun."
Streb, who has not recorded a top-10 finish since last year's US PGA at Whistling Straits, compiled the third 63 in the space of 16 days after Phil Mickelson and Stenson achieved the feat in the Open at Royal Troon.
"I'm happy to join the club that seems to be ever-growing," the 29-year-old said. "Most of the year has been a big struggle. I t's felt like I found something with my golf swing the last two weeks."
Day came into the week "under the weather" and only had one practice round after spending Tuesday evening in hospital after his wife Ellie suffered an allergic reaction.
But the world number one revealed an X-rated pep talk he gave himself after the double bogey on the seventh - where he needed four to get down from a greenside bunker - had done the trick.
"Just a few swear words inside my head, like 'What are you doing?'" the 28-year-old said. "I played that hole so bad that it was really frustrating for me. Why are you doing that? Why are you giving shots to the field when you don't need to do that?"
Source: PA
