By the time the sun broke through in the afternoon, creating postcard views, Brendon Todd tied Day at five under. Almost half of the field was at par or better, including Tiger Woods at 68. Among them were first-round leader Jason Day, who had yet to tee off for his second round.
Meanwhile Koepka, who is chasing history by trying to become the first three-peat PGA major victor in nearly a century, once again demonstrated his ability to raise his game on the biggest stages. Hagen won four in a row from 1924-27, when it was match play.
"Not putting him down or anything, but I thought it was going to be longer", said Adam Scott, who has mostly been watching golf on TV this year and returned to find himself in the same group with DeChambeau.
The field is solid with 95 of the top 100 players in the world expected and Brooks Koepka after two straight wins seek a third, but will have no spectators to cheer him. "I feel like I definitely could have been a few shots lower but I sort of ground it out and with how I hit it on the back nine, even par actually wasn't too bad".
Woods has had four back operations during his career, the latest being a spinal-fusion surgery in 2017.
The first indication that his putter was going to spark was a 32-foot birdie putt on his fourth hole, the 13th, that got him to two under.
The PGA Championship rolls into San Francisco this week as the first major of the year unfolds at TPG Harding Park. He has rarely wavered from the Scotty Cameron Newport II putter that he first put in play in 1999 and used for the next 11 years. It's hard for me to bend over at times, and so practicing putting. "The amusing thing is that every day I'm excited to go back to the golf course and play, whereas before I was struggling to get up and going, 'Do I want to kind of put myself through this again?' To be honest, I'm excited to get out and play every week now". I certainly can't log that with my back being fused.
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Bryson DeChambeau also shot a 68 but he had to overcome an equipment malfunction in the middle of his round when he snapped the head off his driver while leaning on it to pick up his tee. He shot a one-over 71.
"I think that drove me nuts a little bit", said Koepka.
He chatted with a rules official and confirmed that he could legally change out a new shaft, which he did on a later hole. The very next day, Koepka missed the fairway with a drive, and as he was inspecting his ball, he joked with his caddie that there was an ant by his ball, an obvious jab at DeChambeau.
The starter stepped to the microphone and kept to the PGA Championship tradition afforded its champions. That's significantly shorter than the bulked-up DeChambeau's average tee shot - he entered the week leading the PGA Tour with a driving average of 324.4 yards.
"This golf course, you have to hit the ball in the fairway", Woods said.
"It's like pitching in the in the major leagues with a 60-mile-an-hour fastball", said the 5-foot-9, 150-pound Hart.