Alex Smalley made a double bogey at the sixth as German Matti Schmid claimed the lead of the US PGA Championship and Justin Thomas set the clubhouse mark.
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 an extraordinary 21 players were within four shots of his six-under-par score as the final round got under way and the chasing pack began to pile the pressure on.
Thomas, two-time champion, roared into contention and superbly saved par at the last to shoot a brilliant 65 and set the clubhouse lead at five under par – the mark everyone on the course knew they had to beat.
Rory McIlroy, chasing a seventh major and his second in a row, started the day 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.
The Northern Irishman found birdie at the second to move within two. McIlroy was giving himself plenty of birdie chances but they slipped away at four, five and seven as he sat two back.
Two-time major champion Rahm started in fine fashion, birdieing the first two to briefly join Smalley at six under before a poor approach shot at the third brought a bogey.
In just his fifth major, if Smalley was suffering from nerves as the big names closed in he did not show it as he holed a superb 26-foot par putt at the third.
The 29-year-old made par at the first five to remain the solo leader at six under but was struggling off the tee and endured a horror show at the sixth, with two woeful shots from the rough leading to his first double bogey of the week as he dropped to four under.
Moments later, Schmid made his third birdie in the first six holes to take the solo lead, one clear of Thomas, Rahm, former Open champion Cameron Smith and Canada’s Nick Taylor.
But Rahm found trouble at the sixth as he too fell back to four under, alongside McIlroy.
Rai, another underdog battling to see off the heavyweight names, birdied one and four to sit one back at five under before sloppily bogeying the sixth.
World number one Scottie Scheffler began his round five adrift and could not find the fireworks to drag himself back into contention, shooting 69 as his bid for a fifth major fell short.
Should there be a tie at the end of the round, a three-hole play-off will decide the winner of the Wanamaker Trophy.
