South African Aldrich Potgieter grabbed the early lead in a chaotic second round of the PGA Championship on Friday as cold and windy conditions helped cause carnage at Aronimink.
No one was able to pull away from the pack over the sloped greens at the 7 394-yard layout, but the 21-year-old from Pretoria moved to the top with steady play.
Potgieter's five-foot birdie putt at the third hole and three-footer to birdie the par-five ninth lifted him into the lead at five-under.
He could become the youngest 36-hole leader at a major since Tiger Woods at the 1997 Masters.
American Alex Smalley, a back-nine starter chasing his first PGA Tour title, birdied 16 and 18 to seize the solo lead, only to bogey the first three holes on the front side but closed with a birdie at nine to shoot 69 and grab the clubhouse lead on four-under 136.
"A lot of really good moments, some not so great moments, and then a lot of just trying to keep moving forward in between," said Smalley.
"It was difficult, it was chilly this morning, the wind was up. Some of the hole locations are very difficult. They're right on the top of a crown."
Japan's Hideki Matsuyama, who fired 67, and American Chris Gotterup, who closed with three birdies to shoot 65, were finished on 137.
"Just really battled all day," said Gotterup. "It was very hard out there. It was cold. There were some pins it didn't even look like were on the green."
Matsuyama, the 2021 Masters champion, birdied from 23 feet at 13 and 20 feet at seven.
"I played well," said Matsuyama. "This morning was windy. Plus it was freezing cold, and that made it very difficult."
Top-ranked defending champion Scottie Scheffler, third-ranked Cameron Young and fellow American Justin Thomas, a two-time major winner, were in on 138.
Scheffler tumbled from a share of the lead with three bogeys in his first four holes but closed with a birdie at nine to shoot 71.
The four-time major winner missed his first six fairways and seven of 14 overall after hitting 13 of 14 on Thursday.
"It was just really tough," said Scheffler. "It was blowing really hard, and it was quite cold as well. So the golf ball wasn't really traveling anywhere. It was just a really challenging morning overall."
Others were less fortunate.
Germany's Martin Kaymer, a two-time major winner and 18-hole co-leader, made bogeys on five of the first seven holes and shot 75 to stand on 142 with England's fourth-ranked Matt Fitzpatrick.
Ireland's Shane Lowry fired a 76 and looked to miss the cut on 144.
American Patrick Reed, the 2018 Masters winner, shot 72 to stand on 140.
ROSE-Y FINISH
England's Justin Rose chipped in for eagle from 76 feet on his final hole, the par-five ninth, to shoot 73 and looked set to make the cut on the number on 143 despite a day with two double bogeys and four bogeys.
Six-time major winner Rory McIlroy, the reigning Masters champion, birdied two of his first four holes to move inside the cut line.
South African Garrick Higgo, who took a two-stroke penalty for being late to the tee on Thursday, was on time Friday but three bogeys in his first six holes dropped him back.
Late starters included five-time major winner Brooks Koepka, two-time major winner Xander Schauffele, two-time major winner Jon Rahm and three-time major winner Jordan Spieth.
Spieth would complete a career Grand Slam with a victory while Rahm would become the first Spaniard to win the PGA title.