A rejuvenated Lee Westwood set the early clubhouse target as Tiger Woods failed to make an impression on the opening day of the 96th US PGA Championship.
All eyes were on Woods after he declared himself pain free and said he was targeting a 15th major title at Valhalla, despite getting in just nine holes of practice after withdrawing from the final round of the WGC-Bridgestone Invitational with a back injury.
But while the former world number one struggled to a three-over-par 74, Westwood compiled a six-under 65 that was matched minutes later by American Kevin Chappell.
Westwood, who carded a closing 63 at Firestone Country Club on Sunday after missing the cut in his previous four events, looked to have squandered a good start when he covered the back nine in 33 only to run up a double bogey on the first.
However, the 41-year-old bounced back with a birdie on the fourth and rattled in four more in succession from the sixth, ending his round in style by holing from 40 feet on the ninth.
Italian Edoardo Molinari was five under par with four holes remaining, while Holland's Joost Luiten and England's Ian Poulter boosted their Ryder Cup chances with rounds of 68 and Colin Montgomerie returned a highly-respectable 70.
"I wanted to represent the Champions Tour well and 70 is okay to start with," said Montgomerie, who qualified by winning the Senior PGA Championship in May. "I drove the ball well and knew if I did that I could get round."
World number six Matt Kuchar could not say the same thing, the American withdrawing before the start of play with a back injury as the problems mounted for US Ryder Cup captain Tom Watson.
Dustin Johnson has already made himself unavailable for the team due to "personal challenges", while defending US PGA champion Jason Dufner is struggling with two bulging discs in his neck.
Kuchar, who has already sealed his place on the Ryder Cup team for Gleneagles, was replaced in the draw by first reserve John Huh.
Westwood, whose 65 eclipsed his previous lowest score in the US PGA - an opening 66 at Oak Hill last year, said: "Last week was a big week for me.
"Going into last week I felt like I had turned the corner. I was starting to swing it a lot better but that's no good unless you start converting it into low rounds. The first three rounds were frustrating because I played a lot better than three over.
"Then obviously I got it going the final day, shot 63. I tried to keep it low key in the practice rounds here, just playing nine holes each day, and carry that momentum through to the first round, which I've managed to do."
Poulter is another player looking for form after an injury-plagued season, but the 38-year-old looked to have found it courtesy of some lengthy practice sessions this week.
Asked what was most pleasing about his 68, Poulter said: "The overall state of my game, because it hasn't been there for a little while.
"I think the work that I put in Monday, Tuesday, Wednesday was rewarding to go out there to play well. It's the most balls I've hit in any session. The body is allowing me to hit more balls at the minute, which is a good thing. It's coming into the right time of the year."
In contrast Woods was disappointed with his 74, which featured four bogeys and just one birdie, the former world number one chipping in on the 16th.
"It wasn't very good," Woods admitted. "A lot of bad shots and I never got a putt to the hole. I had plenty of looks to turn my round around and then post something even par, even under par. My swing was dialed in on that range out there. Unfortunately, I didn't carry it to the golf course."
Asked about his back, Woods added: "It's a little bit stiff, but that's about it. I'm going to go get treatment and make sure this thing is nice and loose for tomorrow."
The biggest threat to Westwood and Chappell was coming from American Ryan Palmer, who raced to the turn in 31 and remained five under with five holes to play.
But pre-tournament favourite Rory McIlroy was also moving menacingly up the leaderboard, the world number one carding birdies on the fourth, seventh and ninth to reach the turn in three under par.
McIlroy is seeking a third win in succession after victories in the Open and Bridgestone Invitational, not to mention a fourth major title and second US PGA victory in two years.
His serene progress came to a shuddering halt on the 10th, the 25-year-old splitting the fairway with his drive but then hooking his second shot out of bounds.
That led to a double-bogey seven and dropped him back to one under, five behind Westwood, Chappell and Palmer, who had chipped in on the fifth for his sixth birdie of the day.
Sweden's Henrik Stenson and England's Luke Donald were also within striking distance on four under after 11 and nine holes respectively.