Sam Burns matched the 36-hole course record at Riviera on Friday, firing a five-under par 66 to seize a five-stroke lead at the US PGA Genesis Invitational.
The 24-year-old American threatened to run away from a star-studded field with a bogey-free round to stand on 12-under 130 at the halfway mark.
"I was hitting it good and I had some good looks and I was able to convert them," Burns said. "Just had patience out there. I didn't try to force anything. Whenever we were in a tricky spot, just took what the golf course gave us."
World number one Dustin Johnson, the reigning Masters champion, shot 67 to share second on 135 with fellow Americans Tyler McCumber and Jason Kokrak and Chile's Joaquin Niemann.
Three-time major winner Jordan Spieth was on 136 with fellow Americans Max Homa and Wyndham Clark.
Riviera's 36-hole record 130 was set first by American Davis Love III in 1992 and matched earlier by Canada's Mike Weir and Japan's Shigeki Maruyama in 2004.
Burns, chasing his first PGA title, was unfazed at claiming a part of history at the Tiger Woods-hosted event whose prior winners at Riviera include Sam Snead, Ben Hogan, Tom Watson, Nick Faldo, Ernie Els, Phil Mickelson, Bubba Watson and Johnson.
"I don't know, really," he said when asked what the record meant. "We just tried to have a good game plan and stick with it out there all day.
"This golf course doesn't necessarily give you a lot of opportunities, so just put it in the right spots."
Burns began on the back nine with a birdie at the 10th, dropping his approach inside five feet from the cup. He birdied the 12th from just outside five feet and rolled in a 10-foot birdie putt at the par-5 17th.
At the par-5 first, he two-putted from 32 feet for birdie and sank a six-foot birdie putt at the par-3 sixth. Burns made his longest par save at his penultimate hole from just inside 10 feet.
"The save right there on eight, my 17th hole, was big momentum for us," Burns said as the weekend loomed with star rivals in pursuit.
"I'd like to think that I have all the tools to win out here. There are a lot of really good players. I try not to get caught up in that and just try to get better each week."
- DJ likes his position -
Johnson took his lone bogey at the second but responded with a 29-foot birdie putt at the par-3 sixth and closed the front nine with a birdie putt from just inside 20 feet.
He followed with birdies at 10 and 12 and another at the par-5 17th.
"I thought four-under is a really solid score around here anytime. I'm definitely pleased with it," Johnson said. "Still didn't play the par-5s quite as well as I'd like. One-under is not going to get the job done over the weekend. Definitely need to take advantage of the par-5s the next couple days.
"Other than that, I feel like I'm swinging my irons really well, I'm rolling the putter nicely, so looking forward to the weekend. I like my position. I'm five back, but there's only one guy in front of me. I like where I'm at and I do like this golf course and hopefully I can drive it a little bit better on the weekend and give myself a few more chances."
Four-time major winner Brooks Koepka was on 138 while defending champion Adam Scott of Australia made the cut on the number at level par 142.
Rory McIlroy missed the cut for the first time in 26 starts since last failing to reach the weekend at the 2019 British Open at Royal Portrush. Seventh-ranked McIlroy shot 76 to finish on 149.
Reigning US Open champion Bryson DeChambeau missed the cut on 144. Third-ranked Justin Thomas also missed the cut on 150 after a 73.