McIlroy is once again in Schauffele’s rear-view mirror. The world number two, who won his fourth and final major to date at this venue in 2014, started brightly from the 10th with two birdies in his opening four holes.
But a bogey on the 17th was followed by a wayward drive that found water on the par-five 18th. However, McIlroy scrambled a par and that proved the catalyst for a sparkling second nine.
He birdied the first after his second shot from deep rough hit the flagstick and he had a run of three successive birdies from the fifth, including a chip-in from greenside rough on the sixth.
“That was huge,” McIlroy said of his shot into the first hole. “I could have easily bogeyed 18 and been back to even par, and then that ball on one could have hit the flagstick and went anywhere. I could have made bogey from that.
“Potentially being one over par through 10, I’m two under so it’s a three-shot difference. It’s a big swing.”
However, he added: “I’m not really happy with how I played but I am at least happy with the score.”
He was joined on five under by Scotland’s MacIntyre, who followed three birdies on his front nine with two more coming home.
“I had zero expectations,” said the left-hander. “I got off to a nice start and my caddie did well in managing me when I was out of position. But it was just a solid round of golf.”
Cameron Smith, the 2022 Open champion, was among a group on three under, alongside Norway’s Viktor Hovland.
Jordan Spieth, who is making his seventh attempt to become the sixth player to complete the Grand Slam of winning all four majors, started with a solid 69 to be level with his good friend and two-time winner Justin Thomas, who was well supported by his hometown crowd.
European Ryder Cup captain Luke Donald was in the first group out at 07:25 local time and he carded a one-under 70, the same score as fellow Englishmen Justin Rose and Matt Wallace.
Tyrrell Hatton is one further back while Tommy Fleetwood carded a one-over 72.
Tiger Woods, who won the 2000 US PGA title at Valhalla to claim the third leg of what would become his ‘Tiger Slam’, conceded he “struggled from tee to green” after closing with successive bogeys as he also posted a 72.
