JJ Spaun upstaged the world’s best by grabbing a one-shot lead after the opening day of the US Open, as Scottie Scheffler failed to live up to his status as pre-tournament favourite.

Spaun equalled the lowest-ever opening round for a US Open at Oakmont by carding four birdies in a four-under 66, with his impressive start the only bogey-free round on a day where just 10 of the 156-man field finished under par.

The American’s closest challenge comes from Thriston Lawrence, who made six birdies in a three-under 67, while Scheffler, defending champion Bryson DeChambeau and world No 2 Rory McIlroy were all among those to struggle on the opening day.

Scheffler mixed three birdies with six bogeys during a frustrating opening-round 73, leaving him seven back in his bid for back-to-back major titles, with DeChambeau on the same total after three bogeys in his last seven holes.

McIlroy – looking to bounce back from last week’s missed cut at the RBC Canadian Open – was also unable to build on a fast start, having reached the turn in a bogey-free 33, as The Masters champion dropped five shots in the last six holes of a four-over 74.

How Spaun grabbed major lead

Spaun chipped in from off the tenth green – his opening hole of the day – and took advantage of the par-five 12th, with back-to-back birdies from the 16th lifting him to four under and top of the leaderboard.

The world No 25 holed from 11 feet to save par at the first and scrambled brilliantly to close out a blemish-free card, with Lawrence one back after recovering from a mid-round double-bogey to card three birdies on the back nine of an opening-round 67.

“I was actually pretty nervous,” admitted Spaun, who finished runner-up to McIlroy at The Players earlier this year. “I actually tried to harness that, the nerves, the anxiety, because it kind of heightens my focus, makes me swing better.

“I just tried to kind of take what the course gave me. I hit a lot of good shots and tried to capitalise on any birdie opportunities, which aren’t very many out here. But I scrambled really well, too, which is a huge component to playing well at a US Open, let alone shoot a bogey-free round.”

Sungjae Im briefly moved to five under and the solo lead before three late bogeys dropped him back to two under, alongside compatriot Si Woo Kim, with five-time major winner Brooks Koepka producing a birdie-birdie finish to join the Korean pair in tied-third.

McIlroy and marquee names make slow starts at Oakmont

Scheffler – in the afternoon wave – sent an ominous warning to the field when he picked up a shot at the par-four second, only for him to bogey three of his next four holes and cancel out a birdie at the seventh with another dropped shot at the ninth.

The three-time major champion drained a 20-footer at the 11th but three-putted the 13th and missed from three feet to save par at the 15th, with Scheffler’s frustrating round seeing him match the total posted by DeChambeau earlier in the day.

DeChambeau had been under par until he three-putted the ninth and had to hole from the fringe, having taken three shots out of the rough, to get away with a bogey at the par-five 12th.

Last year’s champion also registered successive bogeys from the 15th, dropping him back to three over, with Ryder Cup captain Keegan Bradley and former Masters champion Patrick Reed – who carded an albatross and triple-bogey in his round – also on the same score.

“Just didn’t get anything out of it,” DeChambeau said. “I wasn’t fully on my game. Pretty disappointed with how I played. It’s not too far off. Just got to get the putting a little bit more dialled and I’ll be right there, because three-over could have easily been two-under.”

McIlroy – also out early – made a dream start when he followed a 30-foot birdie at the 11th by firing a 392-yard drive on his way to another at the par-five next, although he sits eight back after carding four bogeys and a double-bogey in a second-nine 41.

Playing partners Justin Rose and Shane Lowry did not fare any better, posting scores of 77 and 79 respectively, leaving plenty of notable names needing to improve on Friday to break into the top-60 and ties required to make the cut.

Who will win the US Open? Watch throughout the week live on Sky Sports. Live coverage continues on Friday from 12.30pm on Sky Sports. Get Sky Sports or stream no contract on NOW.