NEWTOWN SQUARE, Pennsylvania - Overnight co-leader Scottie Scheffler started the second round of the PGA Championship at Aronimink Golf Club with a bogey, as a jam-packed leaderboard sets up an intense day.

The day began with 48 players within three shots of the seven co-leaders: Scheffler, Martin Kaymer, Aldrich Potgieter, Stephan Jaeger, Min Woo Lee, Ryo Hisatsune, and Alex Smalley, all tied at three-under 67.

World No.1 Scheffler’s opening tee shot at the par-four 10th rolled off the fairway. Unable to reach the green with his second shot, his third stopped 19 feet from the hole before he two-putted for bogey.

Kaymer, who won the 2010 PGA Championship before joining LIV Golf, fell back with four bogeys over his first six holes. Smalley played one group behind Scheffler; the other four co-leaders tee off later this afternoon.

Masters champion Rory McIlroy is at risk of missing the cut after a 74, his second opening round of four-over par or worse in a PGA Championship. He tees off at 2:05 p.m. ET.

Two-time major winner Bryson DeChambeau, runner-up in the last two PGA Championships, also needs a strong comeback after a disastrous opening 76.