Russell Henley took the early lead at the U.S. Open, with former world number one Brooks Koepka not far behind, though Phil Mickelson struggled.
Henley shot an impressive four-under-par 67 at Torrey Pines on Thursday to head back in the clubhouse with a one-shot lead over Francesco Molinari and Rafa Cabrera Bello.
Heading in at fourth was four-time major winner Koepka, the 2017 and 2018 U.S. Open champion going round in 69 on the opening day.
Koepka has been involved in one of the big stories in the build-up to the major amid his feud with defending champion Bryson DeChambeau making headlines, albeit the latter dismissed it as "banter back and forth in good fun."
With DeChambeau teeing off later in the day, Koepka set the standard with four birdies in his first 11 holes taking him into a solo lead.
However, two bogeys meant he had to recover with two pars to finish on two under, giving Henley the early advantage.
Ahead of Koepka, Molinari – who has fallen outside the top 150 in the world rankings – was back to his best, with his brother Edoardo just two shots behind on one under.
There was no such luck for six-time major champion and American star Mickelson, whose chances of claiming this elusive tournament look slim.
Mickelson became the oldest major winner when he clinched the US PGA Championship last month, but shot a four-over 75, which included successive bogeys.
Another former US PGA Championship winner to struggle was Collin Morikawa, who also finished on four over.
"It's not the start I wanted, bogeying every par-three, and I think I had like three three-putts today. It's not acceptable," he said.
"It's not how you keep yourself in a tournament on a Thursday. You know what, this course is going to play tough, and still got at least tomorrow to just grind it out and see how it goes. I had some stretches of decent golf, I've just got to keep doing that and really not compound the errors."