American JJ Spaun produced a majestic bogey-free four-under 66 to claim a one-shot first-round lead as only 10 players in the 156-man field broke par on the Open rota's most difficult layout.There were shanks and air-swings from the savage rough as 16 players shot 80 or worse, including American qualifier George Duangmanee, who propped up the field with a 16-over-par 86.
Former world No.1 Adam Scott (70) and the resurgent Marc Leishman (71), playing his first major championship since the 2022 British Open, are the only Australians seemingly still in contention after Cam Davis (74), Cameron Smith (75), Jason Day (76) and Min Woo Lee (77) all struggled.
Heavyweights Scottie Scheffler, Bryson DeChambeau and Rory McIlroy also have work to do to make the halfway cut as Oakmont bared its teeth once more.
Tiger Woods is the only top-ranked player ever to win the Open at the brutal venue, and the curse of the world No.1 struck Scheffler, who could only manage a three-over 73 to be seven shots adrift of Spaun.
Pre-tournament second favourite DeChambeau also opened with a 73, while Masters champ McIlroy is one stroke further back, right on the cut line in a tie for 62nd, after shooting 41 on his inward nine.
"It got me," said defending champion DeChambeau.
"Even for a guy like me, I can't get out of it some of the times, depending on the lie. It was tough. It was a brutal test of golf."
Scott is tied for 11th after grinding out an even-par round despite suffering another dispiriting late lapse after a rousing early-morning effort on Thursday (Friday AEST).
The 44-year-old was right in the thick of the hunt for the clubhouse lead as he reached the turn in two under after racking up five front-nine birdies.
But dropped shots at the third and eighth holes - his 12th and 17th after starting from No.10 - dragged the veteran back to level par, four shots adrift of Spaun.
Monday qualifier Leishman hit only three fairways but scrambled brilliantly to grab a share of 20th spot.
Mixing five front-nine birdies with three bogeys, 2013 Masters champion Scott's round was a topsy-turvy affair from the start.
The 34-year-old Spaun, who lost to McIlroy in a play-off at The Players Championship in March, recorded his lowest ever round in a major to nab a one-stroke advantage over unheralded South African Thriston Lawrence.
Spaun, who started on the back nine, had a spectacular start reaching the turn with four birdies to become the first player ever to cover the first nine in the opening round of an Oakmont US Open in 31 strokes or fewer.
Two-time US Open winner since Brooks Koepka is well poised in a tie for third at two under with South Koreans Si Woo Kim and Sungjae Im.
Im got to five under to briefly enjoy the outright lead before three late bogeys left him to match Koepka's 68.
In-form Ben Griffin, fellow American James Nicholas and Belgian Thomas Detry, Spain's two-time major champ Jon Rahm and Dane Rasmus Neergaard-Petersen all posted 69s to be the only other players in red numbers.
The shot of the day was Patrick Reed's amazing second on the 621-yard fourth hole, which the former Masters champ holed from 286 yards for only the fourth albatross in US Open history.
With agencies
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