A week after announcing that he had parted ways with his 20-year coach and mentor Col Swatton, Day continued the play that saw him log three top-10 finishes on the PGA Tour at his last three starts.

Although two years have passed since his most recent win, Day came in confident and did not make a single bogey at TPC Harding Park in San Francisco.

At five-under, he is tied with American Brendon Todd, who by chance has an Australian swing coach (Bradley Hughes) and who came in late with his own 65.

They are a shot ahead of a bunch at four-under that includes former world No. 1s Brooks Koepka and Justin Rose at 66 and major champions Zach Johnson and Martin Kaymer. Tiger Woods started nicely with a 68.

As a nice exclamation point for his first round Day hit a five iron to the shadow of the flag stick at the par-four ninth hole and rolled in his fifth birdie of the round to finish.

That came after two good opportunities missed on the seventh and eighth greens, but Day kept his perspective. “Once again, I finally had enough of feeling sorry for myself, and it’s easy to do that in this game because it is so mentally tough,” he told the media afterwards. “You can start blaming everything else but yourself. Sometimes you’ve just got to pull your pants up and just move on, you know.

“I feel like the momentum that I’ve had over the last three starts has kind of seeped into this week. I’m excited about — the funny 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, ‘oh, 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.’’

Day appreciated the appearance of the sunshine to help him with his sore back. “I pretty much lather up in Deep Heat and I go — I mean, I try and burn the skin off my back, to be honest. And I feel pretty good, so I’ve been fine.’’

The season’s first major in San Francisco played out to the surreal atmosphere at Harding Park with no fans. As a few of the players have said, it is far from what they are accustomed to.

“I actually miss playing in front of fans because you obviously work off that, especially in a major championship,” said Day. “You work off that energy. Usually it’s buzzing, and it happens from Monday all the way through to Sunday. It’s just a lot of people here. There’s a big buzz going around the golf course.

“And today, we’re used to it by now, but it’s still not the same. I know that we are playing the PGA Championship. It’s a major championship. It’s the first one of the year. It’s still just not the same.”

Day, who is ranked 42^nd in the world, won the 2015 PGA Championship, his only major victory. His round today was his first bogey-free round in a major since 2017.

Adam Scott (68) was the best of the other five Australians, making his first tournament start since the Covid-19 induced interruption to the tour. Matt Jones and Marc Leishman both cobbled even-par scores, while Cameron Smith (71) and Lucas Herbert (73) have work to do.