Rory McIlroy battled illness and a poor start to remain in contention for a third US PGA title as Eric Cole leads at Oak Hill.
Starting on 10th, McIlroy's round appeared to be in danger of unravelling with three bogeys in four holes between 15 and 18.
Sitting on three-over, his third shot to the par-four second charged through the back of the green, running down the steep slope behind. Saving bogey appeared a tall order but McIlroy proceeded to hole out audaciously from 35 feet for an unlikely par, much to his relief and even amusement and to the delight of the whooping galleries.
He then hit a brilliant tee shot to two feet on the next on his way to back-to-back birdies.
"It was massive," McIlroy said. "I was sort of just hoping to get down in two and make bogey and go to the third hole at four over par.
"When you walk off the green three over and then you hit a tee shot like that, all of a sudden the pendulum swings or momentum goes the other way and you feel like you're right back in the tournament.
"Depending on what happens over the next three days and what I go."
McIlroy reduced the 617-yard fourth hole to a drive and long iron to set up his second birdie of the day and although he three-putted the next, a birdie on the eighth helped complete a battling round despite being under the weather.
"I'm fighting something," McIlroy said post-round.
"I thought I got a great night’s sleep last night and I looked at my Whoop (personal fitness monitor) and I was 22% recovery, and my skin temperature was 3.5 degrees higher than what it’s been.
"But I actually feel better today than I felt yesterday, so plenty of water and a bit of rest, I’ll be fine."
Shane Lowry endured a frustrating afternoon, posting a three-over par 73 to sit seven adrift of the early leaders.
After a steady start, he found the bunker shy of the green at the intriguing short par-four at 14. There was a prolonged wait as his playing partners Jordan Spieth and Viktor Hovland played from a near-identical position.
Ultimately, Lowry wound up blading the pitch, running through the green and scooting down the downslope behind the green. Almost inevitably, his third ran down to the front of the green, whereupon he two-putted for bogey.
Another bogey followed on 17, though he got a boost around the turn, with a remarkable 52-foot putt for birdie on the first. Eschewing the wedge, Lowry rolled it up the slope to the right of the green, allowing it feed down to the hole for birdie.
A poor pitch cost him a stroke at the third and a wayward drive resulted in a finishing bogey at nine to leave him on three over heading into Friday.
The 2008 champion Padraig Harrington, who memorably finished tied-fourth at Kiawah Island two years ago, posted a respectable round of 72.
The Dubliner showed his renowned scrambling skills, making improbable par saves throughout, notably on the 18th.
Seamus Power was among the last eight, reaching the turn at +3. The Waterford native began with a birdie, but two bogeys and a double bogey in his next four holes halted that early momentum and the Waterford native ended on five over par.
Bryson DeChambeau set the clubhouse target at Oak Hill.
On a course which has drawn comparisons to Winged Foot, the venue for his US Open triumph in 2020, a slimmed-down DeChambeau still possessed enough power to post six birdies and two bogeys in an opening 66.
That gave DeChambeau a one-shot lead over world number two Scottie Scheffler, Dustin Johnson and Corey Conners, with Viktor Hovland, Ryan Fox, Keegan Bradley and Adam Scott on two under par.
American Cole had reached five under par after 14 holes before play was suspended due to darkness, the result of a delay of almost two hours caused by frost on Thursday morning.
"It's a fantastic round of golf at Oak Hill," DeChambeau said. "It’s a prestigious place. Very difficult golf course.
"As I was looking at it throughout the week, I’m like, man, I don’t know how shooting under par is even possible out here on some of the golf holes.
"It’s a different test (to Winged Foot) and a test that I’m willing to take on. If you’re driving it well and hitting your irons well, you can play out here, but it can get pretty nasty pretty quick if you’re not hitting it straight."
Masters champion and world number one Jon Rahm surprisingly slumped to a six-over-par 76.
Rahm had started his day with a birdie on the 10th, his opening hole, but dropped five shots in six holes around the turn and also made a double bogey on the seventh.
"Obviously the first six holes of the day I played really good," Rahm said.
"Put myself in a good spot and after that I found myself battling. Couldn’t find the fairway and the fairways that I missed cost me bogeys."
