KIAWAH ISLAND, S.C. — One hole into the PGA Championship, Brooks Koepka was more worried about his brain than his ailing knee.

His opening tee shot on the 10th hole at Kiawah Island was struck poorly and didn’t quite clear a waste area. Koepka tried to do too much from a soft lie in the sand and barely got it out. It led to a double bogey, and the toughest part of the Ocean Course was still to come.

But this is a major, and this is Koepka, and that’s when he’s at his best. He knuckled down from that mess by running off six birdies the rest of the way for a 3-under 69 and a share of the early lead Thursday.

“The first rule is, if you’re in trouble, get the hell out. So mental mistake there. I deserved every bit of that double bogey,” Koepka said. “I can’t play with any mistakes, maybe one a day, and that was my one. And I got it out of the way.”

The wind was stiff enough that only four of the 78 players in the morning wave broke 70, and only a dozen others managed to break par.

Keegan Bradley, a PGA champion from 10 years ago, was one of only three players to get as low as 4 under in the morning before making a mistake, which was inevitable on this course. Bradley also shot a 69, along with Viktor Hovland of Norway and Aaron Wise.

Koepka wasn’t alone in the odd blunder. He was among the few who recovered.

Justin Thomas was going along nicely on the back nine until he had trouble getting out of the sand and then chopped his way through the rough for a double bogey on the 18th hole. Two holes later, he sent a sand shot over the green and just into a hazard for another 6 on the par-5 second. He shot 75.

Rory McIlroy, coming off a victory at Quail Hollow two weeks ago, sent his opening tee shot into a water hazard some 30 yards right of safety. He salvaged a bogey, but certainly not his round. McIlroy made bogey on three of the par 5s for a 75, his worst start ever in a PGA Championship.