Rory McIlroy’s hopes of a second major victory of the year suffered a significant setback after a nightmare finish to his opening round at the US Open.

McIlroy has struggled for consistency and motivation since completing the career Grand Slam in April, coming into the third men’s major of the year with a tied-47th finish at the PGA Championship and a missed cut at the RBC Canadian Open.

The Masters champion briefly shared the lead after two birdies in his first three holes at Oakmont Country Club on Thursday morning, where he reached the turn in 33, only to drop six shots in an eight-hole stretch leaving him signing for a four-over 74 and eight strokes behind clubhouse leader JJ Spaun.

McIlroy followed a bogey at the par-four first with three more in a four-hole stretch from the fourth, with a double-bogey at the par-three eighth.

The Northern Irishman elected against speaking to the media post-round, with McIlroy – who has finished no worse than ninth in his past six US Open appearances – needing improvement on Friday to have a chance of making it through to the weekend.

He was not the only player to struggle in the morning wave, where just five players finished under par, with defending champion Bryson DeChambeau carding a three-over 73 and Shane Lowry – playing alongside McIlroy – stumbling to a nine-over 79.

A tale of two nines for McIlroy

McIlroy – beginning on the back nine alongside Ryder Cup team-mates Shane Lowry and Justin Rose – failed to capitalise on a 10-foot birdie opportunity on his opening hole but made amends by draining a 25-footer at the par-four next.

A 392-yard drive – his longest of the season – helped McIlroy to a two-putt birdie at the par-five next, briefly moving him into a share of the lead, with impressive par saves at the 15th and 17th helping the world No 2 reach the turn bogey-free in 33.

McIlroy’s struggles began with a three-putt bogey at the par-four first, he then holed from 30 feet to limit the damage to a bogey at the par-five fourth after taking three shots to gauge out of thick rough.

He fell further behind when he failed to get up and down from the greenside bunker at the par-three sixth, missing from six feet, with McIlroy then three-putting at the par-four next to card a fourth bogey in seven holes.

McIlroy left his ball in the rough on his way to a double-bogey at the long par-three eighth, dropping him to four over, with his slow start the first time since 2018 that he has carded an over-par opening round at the US Open.

Only three of the last 26 US Open champions have not been within four of the lead after the opening round of a US Open, although McIlroy – eight back – came from seven behind after 18 holes to win his elusive fifth major title at The Masters earlier this year.

What went wrong for DeChambeau and McIlroy?

Sky Sports’ Paul McGinley, reflecting on disappointing starts for DeChambeau and McIlroy:

“I actually thought Bryson [DeChambeau] played quite well. He just putted really poorly for him, otherwise he’d have been hovering around even par.

“You’re not going to discount him [on three over]. I think he will find his putting over the next three days. He has hit more fairways than he did at the PGA Championship and at The Masters, which is a big improvement.

“We saw a huge improvement in his iron play, too, so he looks to be on it if he can get his putting going. I wouldn’t be too concerned about him but for Rory, he had a really poor back nine.

“McIlroy didn’t play that badly but his iron play let him down – he was in the bottom 10 per cent for iron play in the opening morning and you’ve got to be good around here with your irons.

“Even though the targets are big in size, in reality they’re small because they’re on little pimples. If you miss it in the wrong spot, you’re going to pay the price and McIlroy did that several times.”

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