Matthew Wolff, a 21-year-old American making only his second major start, fired a five-under par 65 to seize the clubhouse lead in Saturday's third round of the US Open.
The 2019 US college champion for Oklahoma State, who shared fourth at last month's PGA Championship in his major debut, solved wicked Winged Foot to stand on five-under 205 after 54 holes.
"Every time I was in the rough and had a good lie I took advantage of it," Wolff said. "I minimized the mistakes. It was a good day all around."
South Africa's Louis Oosthuizen, the 2010 British Open champion, fired a 68 to stand second in the clubhouse on 209 with American Bryson DeChambeau the only under-par rival still on the course at two under.
"Any under-par round at a US Open you'll take," Oosthuizen said. "(Wind) definitely died down for us. Definitely lucky on the draw today."
World number 36 Wolff, who won his first PGA Tour title at Minneapolis in only his third tour start, needed only 10 putts over his first nine holes, shooting a astonishing 30 on the front nine as veteran rivals struggled on the famed Mamaroneck, New York, layout.
He found only two of 14 fairways but made impressive iron shots to match Winged Foot's lowest US Open round ever, Justin Thomas's opening 65.
"I tried to shoot as low as possible with hitting as few fairways as possible," Wolff joked. "That will get me ready for tomorrow.
"I got really fortunate with the lies in the rough. I just stuck with my game. We had a bunch of good lies. It was a grind out there.
"I'm just going to go out there, do the same thing and whatever happens happens."
Wolff, who began the day four back of leader Patrick Reed, made a 14-foot birdie putt at the opening hole, a 15-footer to birdie the par-4 fourth, a five-footer for birdie at six and a 13-foot birdie putt at the par-3 seventh.
He closed the front nine with a three-foot birdie putt at the par-5 ninth then grinded out six pars in a row before his first bogey at the 16th, missing an eight-footer for par.
Wolff blasted out of the rough 10 feet from the cup at 18 and sank his closing birdie putt.
"I feel really good with my putting," Wolff said. "I just told myself it was just another putt."
Oosthuizen sank an eight-foot birdie putt at the fifth and added eight pars on the front nine. On the back side, he followed a bogey at the par-3 10th by sinking an 18-foot birdie putt at 11.
At 14, Oosthuizen blasted out of the rough to 10 feet and made his birdie putt, then found rough and a bunker to bogey 16 before dropping his approach at 17 to three feet and making another birdie in response to a bogey.
Oosthuizen suspects he will need a repeat performance to capture his first major in a decade.
"I need to play pretty similar to what I did today," he said. "A lot can happen even in the last two, three holes, so try and get yourself in a position with three, four, five holes to go and see what you can do.
"Just need to go out and play some good golf tomorrow."
- McIlroy, Matsuyama lurk -
Japan's Hideki Matsuyama, who made four birdies and three bogeys in his first seven holes, scrambled to a 70 to stand alongside American Xander Schauffele on level par 210.
Matsuyama, chasing his first major crown, opened with a birdie, followed with back-to-back birdies, then reeled off three birdies in a row on putts inside eight feet before a three-putt bogey at the par-3 seventh.
The Asian star birdied the par-5 12th and 14 but a bogey at 15 was followed by a double bogey at 17 after finding deep rough and a bunker.
"I made a lot of birdies, but hopefully tomorrow I can make the same number of birdies without the bogeys," Matsuyama said. "I hit some good putts today, but at the same time I hit some bad ones. Tomorrow I just pray that I have more makes."
Four-time major winner Rory McIlroy was next in the clubhouse on 211 after a third-round 68, liking his chances of winning his first major title since the 2014 PGA.
"I'm feeling pretty good that I've got a good chance going into tomorrow," McIlroy said. "(Six) is not a lot on this golf course. I feel like I'm right in it."