Scheffler was one of the last groups out at Aronimink Golf Club in south-west Philadelphia, on a day where low scoring had proved elusive.

He ended it three under, part of a seven-way group at the top of a congested leaderboard which featured German Martin Kaymer, 12 years on from the last of his two major wins.

A record 33 players are within two shots of the lead, eclipsing the previous high of 28 at the 1993 Open, including 12 major champions.

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Scheffler started steadily but dropped a shot at the fifth. He made his move with back-to-back birdies at six and seven before salvaging par after chipping out of the greenside bunker at the monster 245-yard par-three eighth.

A third birdie came with a 28-foot putt on 10 to move two under and he joined the leading pack with another at 11.

Scheffler, in his 156th consecutive week as world number one, had cut a frustrated figure across the front nine but his move up the leaderboard had an air of inevitability.

A birdie on 16 cancelled out a bogey on 14 and ensured the four-time major winner held at least a share of the lead after the first round of a major championship for the first time.

The defending champion was in a strong trio alongside world numbers four and seven Matt Fitzpatrick and Justin Rose.

Rose bogeyed three and six but dug in and got his reward with a birdie at 13 followed by another at 14 as he chipped in from the bunker to delight the gathered crowds.

Fitzpatrick started with 13 straight pars before a bogey and a birdie also left him at even par.

Major winners Xander Schauffele, Patrick Reed and Shane Lowry – who chipped in for an eagle on nine – are a shot off the lead.

Nobody was able to break clear of the pack with a low score as Aronimink bared its teeth and allayed fears that it would not test the world’s best golfers.

The enormous, undulating greens proved a stiff examination, making avoiding bogeys feel like the priority.

McIlroy had felt it would be a “bash driver down and figure it out” course, but he more than most, paid the price for straying into the rough, admitting it was more penalising than he expected.

The Northern Irishman, bidding to win back-to-back majors and a seventh overall, finished his round with four successive bogeys and five out of the last six as wayward tee shots decimated his card to leave him four over.

After bogeying the first and birdieing the second, McIlroy reeled off 10 straight pars before a rollercoaster back nine left him with work to do.

As the late starters began to turn for home, McIlroy was on the practice range trying to find the answer to his driving issues.

His playing partners Jon Rahm and Jordan Spieth are among the vast group at one under par. Rahm pitched in from 98 yards for eagle at the second, his 11th, to banish a frustrating start and finished with consecutive birdies.

Selected round two tee times

11.45am – Dustin Johnson, Rasmus Hojgaard, Michael Block (hole one, all times BST)
1.07pm – Viktor Hovland, Collin Morikawa, Shane Lowry
1.18pm – Robert MacIntyre, Tommy Fleetwood, Chris Gotterup
1.29am – Justin Thomas, Cameron Young, Keegan Bradley
1.40pm – Scottie Scheffler, Justin Rose, Matt Fitzpatrick
6.54pm – Xander Schauffele, Brooks Koepka, Tyrell Hatton
7.05pm – Rory McIlroy, Jordan Spieth, Jon Rahm.