Rory McIlroy was among the five-man pack sitting one shot back of Canada's Adam Hadwin after the first round of the US Open on Thursday as Phil Mickelson struggled a week after making his controversial LIV Golf debut.
Mickelson shot an eight-over par 78 to sit near the bottom of the 156-player field at The Country Club.
A record six-time US Open runner-up, Mickelson's self-imposed four-month hiatus following comments he made about the LIV circuit and PGA Tour was evident in the opening round.
Mickelson, who struggled on the greens all day, added another double-bogey at the 12th hole before closing another bogey on a day when his latest bid for the career Grand Slam effectively came to an end.
McIlroy, who came into the year's third major fresh off a successful title defence in Canada, went out early and shot a three-under-par 67 and maintained a clean scorecard until a bogey at the final hole.
That left McIlroy level with Englishman Callum Tarren, Swede David Lingmerth, American Joel Dahmen and South Africa's MJ Daffue.
A month after an opening 65 in the US PGA, it was another welcome start to a major for McIlroy after previous struggles, but it was not without incident as he slammed one club into a bunker and threw another down the fairway on his final hole.
After starting from the 10th, McIlroy had covered his first 13 holes in two under par before a pushed tee shot on the fifth finished in thick rough on the edge of a bunker and left him struggling to take a stance in the sand, with the ball well above his feet.
From there McIlroy could only hack his second shot into another bunker a few yards in front of him, prompting a furious reaction which saw him twice slam his club into the sand.
"You're going to encounter things at a US Open that you just don't really encounter any other week," said McIlroy.
"It's hard not to get frustrated because I'm walking up there going like, just come back into the bunker. The thickest rough on the course is around the edges of the bunkers.
"So I was sort of cursing the USGA whenever I was going up to the ball, but it's one of those things. It happens here, it doesn't really happen anywhere else. You just have to accept it.
"I gave the sand a couple of whacks because I'd already messed it up, so it wasn't like it was much more work for Harry [Diamond, his caddie], and then I just reset and played a decent bunker shot, and then it was really nice to hole that par putt."
Meanwhile, Hadwin compiled five birdies in a six-hole stretch to make the turn at 4-under 31. That included three straight birdies, with his second shot at the par-4 ninth rolling to inside three feet of the pin.
After a bogey at the 12th, Hadwin recovered with a birdie at the next to re-establish himself as the sole leader.
"Not much better of a start to a U.S. Open ... that you can ask for," Hadwin said. "I did a lot of good things. Got on a nice run there midway through the front. Then I kind of just held down the fort there the last little bit. Some key up-and-downs. Made a nice one from the fringe on 13. Just doing a lot of good things."
Hadwin, 34, earned his only PGA Tour victory in 2017. He has never finished inside the top 20 at a major.
"Sixty-six at a US Open to take the first-round lead is incredible," Hadwin said. "It's amazing. It's something ... nobody can ever take away from me at this point, but I have bigger things in my mind."
