Tiger Woods made a steady start to his quest for a fifth US PGA Championship but an eye-catching 66 from Brooks Koepka suggested history could be made this weekend in San Francisco.
A two-under 68 from Woods meant the 44-year-old was three shots off the early clubhouse pace set by Jason Day at TPC Harding Park, in golf's first major of the disrupted 2020 season.
Koepka was only one behind Day, however, raising the prospect of a title challenge from the man who is chasing a hat-trick of consecutive US PGA titles.
Woods has twice triumphed at the US PGA in consecutive years (1999-2000, 2006-2007), but nobody has taken the title three years in succession in the stroke-play era.
That is the challenge Koepka is embracing, with the 30-year-old recovering well after dropping a shot at his second hole, having started on the back nine.
Koepka said on Sky Sports: "I just keep playing one shot at a time, one hole at a time, keep plugging away. I'm playing so good that... I hit a good putt at 11 and it just didn't go in, I just over-read it a little bit, but other than that I played everything pretty much how I wanted to. I played really well."
Koepka had been struggling for form since the PGA Tour returned until tying for second last time out at the WGC-FedEx St. Jude Invitational.
He had a closing 80 at the Memorial Tournament and missed the cut at the Workday Charity Open and 3M Open, but Koepka loves to produce on the big stage.
"It's a major, I'll get up for it," Koepka said. "It's a little bit of confidence I guess, maybe a little bit, but at the end of the day I just feel good, I'm playing good, and there's no reason to be scientific with all the numbers and stuff. You just go out and play."
Koepka, playing two groups ahead of Woods, parred his way home after making birdie at two and four – his 11th and 13th holes.
By contrast, there was anguish across Woods' face as he missed a par putt at the eighth – his 17th hole – after a brilliant bunker shot, knocking him back from three under.
Woods, nonetheless, was happy with his efforts, and felt scoring would become tougher later in the day due to increasing winds.
The tournament was being played without spectators, meaning there was no crowd energy for the players to feed off, nor any familiar applause as they were introduced for the start of their rounds.
Asked if he was satisfied with how he played, Woods said: "Yeah, I was. I figured we were going to get the more favourable of the conditions today, with the wind supposed to pick up, which it is now.
"The golf course is only going to get more difficult.
"Some of these pins were a little on the difficult side, but overall this golf course is all about hitting fairways, and if you're able to hit the fairway you can get after some of these flags."
Woods was playing with a new putter for the first time, and said: "I've been messing about with it for the better part of over a year.
"It's a little bit longer than my original one, which makes it a little easier on my back. I was able to spend more time practising."
Koepka had plenty of company at four under, with Americans Scottie Scheffler, Xander Schauffele, Zach Johnson, Bud Cauley and Brendan Steele all on the same mark through 18 holes, along with Englishman Justin Rose and Germany's 2010 US PGA winner Martin Kaymer. France's Mike Lorenzo-Vera also had a 66.
Australian Day, the 2015 champion, could not be matched though, with five birdies and no dropped shots setting the standard.
Rory McIlroy, the 2012 and 2014 US PGA winner, was grouped with Woods and world number one Justin Thomas, who won this tournament three years ago. McIlroy had a level-par 70 and Thomas a frustrating one-over 71.