The defending champion was the leading name among a seven-way tie for the lead – the first time he has led after an opening round of a major in his career – as the second day began in south-west Philadelphia.

The 29-year-old started shakily to slip off the lead and he was far from alone as dropped shots littered the card.

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The early-morning struggles may have lifted the spirits of Rory McIlroy, who ended day one seven shots back after what he described as a “s***” opening round.

The Northern Irishman, chasing a seventh major title, knows he has plenty to do to fight his way back into this championship but at least the leaders were not pulling out of sight. He is among the last to go on Friday, at 2.05pm local time (7.05pm BST).

Aronimink provided a stern opening-day test for the world’s best, with nobody able to break clear of the three-under mark as a record 33 players stood within two shots of the lead – with 12 major champions among them.

The first of the leaders to try and break free was German Martin Kaymer, bidding to recapture major glory 12 years on from the last of his two successes, but two early bogeys sent him backwards.

More European hopefuls took to the course on the back nine, Shane Lowry bogeying his opener from a shot off the lead as did Robert MacIntyre to drop to one over.

With low scoring still proving elusive, focus turned to Scheffler – also on the back nine in a strong group alongside Matt Fitzpatrick and Justin Rose who both started at level par. All three found trouble.

Rose found the fairway bunker at 10 and his escape attempt smashed into the face and remained in the sand, resulting in a double bogey opener.

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Scheffler and Fitzpatrick both missed lengthy par-saving putts as both opened with a bogey.

The world number one found the rough off the tee at 12 and could only hack out on his way to a second dropped shot, while a beautiful approach had Rose moving back in the right direction.

Up ahead, two-time champion Justin Thomas was undone by the undulating green at 11 and it was back-to-back bogeys after missing on 12.

Patrick Reed birdied his fourth hole to join the leaders at three under. The 2018 Masters champion was the only player in field yet to record a bogey in the tournament.

But not for long, as a dropped shot at the fifth pegged him back again.

The congested leaderboard means McIlroy at four over is among those with work to do to make the cut. It is set to be 70 players and tied who will reach the weekend, which early on Friday stood at two over.