Smalley, without so much as a PGA Tour win to his name, took a grip of the championship on Saturday evening as he birdied four of the last six holes to pull two shots clear of the pack at Aronimink Golf Club.

But, with an extraordinary 21 players within four shots of his six-under-par score, including a host of major champions, it was a question of who could make a charge.

N/A

McIlroy, chasing a seventh major title and the second in a row, started three back and one adrift of a crowded group at four under – which featured two-time major champion Jon Rahm, England’s Aaron Rai and Sweden’s Ludvig Aberg.

World number one Scottie Scheffler was struggling to find the fireworks he needed to slash his five-shot deficit.

Teeing off two-and-a-half hours before Smalley, a birdie at the second was wiped out by a bogey at the fifth but he picked up another at the ninth to turn four adrift.

Hideki Matsuyama, the 2021 Masters champion, was the first to make a serious move with three birdies from the first five taking him level with the ever-growing group two back at four under.

He was joined there by former Open champion Cameron Smith, two-time winner Justin Thomas and Friday’s overnight co-leader Maverick McNealy, before a bogey at the seventh checked Matsuyama’s progress.

Justin Rose, who only made the weekend thanks to a stunning chip-in eagle at the last on Friday, opened with a birdie to move three back – following a brilliant 65 on Saturday – as McIlroy walked to the first tee.

He and playing partner Xander Schauffele, the 2024 champion, both found the rough at the first but McIlroy sunk a testing par putt.

American Kurt Kitayama had earlier showed what was possible as he carded the best round of the week with a seven-under-par 63, the joint-lowest final round in major history, to set the clubhouse lead at three under.

England’s Matt Fitzpatrick, who was one of the pre-tournament favourites after winning three times on the PGA Tour this season, ended a tough week on a high note with a five-under 65.