Top-ranked Scottie Scheffler and world number two Jon Rahm were set for early starts as Thursday's first round of the 123rd US Open began at Los Angeles Country Club.
The event is the first major golf tournament since the last week's surprising news that the PGA Tour and DP World Tour would unite with the Saudi financiers of the upstart LIV Golf League.
That will make for a spicy afternoon group with Brooks Koepka, last month's PGA Championship winner as the first LIV Golf member to capture a major, joined by Rory McIlroy, the PGA Tour's most vocal defender, and Japan's Hideki Matsuyama, the 2021 Masters champion.
Koepka, a five-time major winner, won the 2017 and 2018 US Opens and was second at the Masters in April before taking his third PGA crown. He has been on fiery form this year, showing no sign of woes from playing 54-hole LIV events.
"I'm pretty sure I know what it takes to compete in majors," Koepka said.
The tension will begin early as Scheffler, last year's Masters winner, goes off the first tee in the ninth group with California favorites Max Homa and Collin Morikawa, a two-time major champion.
Scheffler is the rare player with experience on the course, having helped a US team beat Britain and Ireland over the layout in the 2018 Walker Cup amateur matches.
Homa, a six-time PGA Tour winner, set a course record of 61 in winning a 2013 Pacific-12 collegiate championship.
Spain's Rahm, who won the 2021 US Open down the coast at Torrey Pines, captured his second major title at this year's Masters and has won four events this year in all, including the Tournament of Champions and two California events, the American Express and Genesis Invitational at nearby Riviera.
Rahm, who could overtake Scheffler for world number one with a victory or runner-up finish, is in the 10th group off the 10th tee along with in-form Norwegian Viktor Hovland and American Xander Schauffele.
Defending champion Matt Fitzpatrick of England will start in the afternoon alongside Cameron Smith, the reigning British Open champion, and American Sam Bennett, who turned pro after earning low amateur honors at the Masters.
Other early starters Thursday include two-time major winner Justin Thomas, 2019 British Open champion Shane Lowry of Ireland and England's Tommy Fleetwood.
Two groups ahead of Rahm will be 2013 winner Justin Rose, former world number one Jason Day and Rickie Fowler.
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