Rory McIlroy was disappointed to miss out on a magical 59 but thrilled to fire an eight under 62 and share the first round lead with Tiger Woods in the BMW Championship in Philadelphia.
The world number eight took advantage of wide fairways and soft greens to race to nine-under par with four holes to go at par-70 Aronimink.
But while he bogeyed the seventh and eighth before finishing with a birdie four to join Woods on eight-under-par, just one stroke clear of US Ryder Cup wildcard hopeful Xander Schauffele, he was excited to see the hard work he's done on his game pay off since skipping the first FedEx Cup event.
“Yeah, I am a little disappointed," said McIlroy, who shot an eight-under 27 for his last nine holes in the pro-am and was 17-under for 23-hole stretch.
"Getting to nine under par with four holes to play with two of those short par fours and the last hole a par-five, you are not going to get many chances to shoot sub-60 and today I had a chance, and I didn't take advantage of it.
"But I won't dwell on that too much. It was still a really good round of golf. I am very happy with how I played and it's set me up great for the rest of the week."
Starting on the back nine, the Co Down star made a hattrick of early birdies from the 11th but didn’t have to make a birdie putt outside nine feet after that as he reeled off six a row with a brilliant display of driving and short iron play — his Achilles’ heel in recent months.
After making birdie at the 18th to turn in 31 and then picked up shots on his first five holes coming home before following bogeys at the seventh and eighth with a two-putt birdie four at the ninth.
“It is trending,” said McIlroy of his game. “I took the first FedEx Cup event off to work on my swing, and I feel like it is coming around.
"I changed golf ball to a slightly softer, spinnier golf ball, the TP5 and that has helped the approach play a little more. I've been able to flight it a little bit lower and have a little bit more control.
"Overall everything is pretty good and I have an opportunity to go out tomorrow to shoot another good one. I am in a great position going into the next few days."
He admitted it would be “awesome” to go head to head for the title with Woods, who put his trusty Scotty Cameron putter back in the bag and racked up an eagle, seven birdies and just one bogey at the 17th hole in his 62.
"I've been monkeying around with it back home and in the backyard," Woods said of his decision to go back to his favourite putter.
"I know the release point and I know how it swings, and my body morphed into a position where it understands where it needs to be to release the putter."
McIlroy wasn't surprised he played well yesterday after burning it up in the Pro-Am.
"So, I guess I went out and played 9 holes with Tiger on Tuesday, the front-9 and then the Pro-Am yesterday I started on 10 so I hadn't played that 9 and I played that 9 holes of golf and said to, 'Harry, this 9 seems a little tougher than the front-9, seems like a few more chances on the front-9.'
"Going to the front-9, the last nine of the Pro-Am and I make 7 birdies in a row. And then I parred it and birdied 9 and shot 27. Then I go on today and play my first 14 in 9-under par. So I played -- I played the 23 hole stretch in 17-under par. Oh, that's pretty good.
"But, yeah, like it's a golf course where big wide fairways, if you carry it 300, 310 off the tee it's a massive advantage and it's a golf course that just seems to fit my eye."
McIlroy's short iron play was excellent and he was proud to take something off a nine-iron from around 140 yards on one hole and play a low spinning shot with a club he normally hits over 160-165 yards.
"I just took a little bit off it, just trying to play feel shots, especially into back pins," McIlroy said. "I don't want anything spinning away. Just getting back to playing shots like that. I have practised that shot a lot."
As for his habit of putting in good performances in the Playoffs, especially in years when he hasn't won a Major, he said: "I think sometimes, if a Major season doesn't go your way and you haven't done what you wanted to it's just a bit of a reset, let's go again, re-assess your goals. I guess that's what I did.
"I took Northern Trust off to work on a few things. I really just wanted to get my game ready for these few weeks and obviously leading up to the Ryder Cup as well. I think a round like this, it sets me up for another run at the FedExCup and hopefully I can continue on from here and play well and give myself a better chance going into East Lake. I'm happy with where I'm at."
On the European Tour, Paul Dunne found just three fairways as he opened with a one-over 71 in the Omega European Masters at Crans-sur-Sierre.
He’s tied for 81st, seven shots behind Germany's Maximilian Kieffer, who fired a six-under 64 for a one-shot lead over Frenchman Julien Guerrier, Dane Søren Kjeldsen, England's Andy Sullivan and Japan's Hideto Tanihara.
In the Challenge Tour's Bridgestone Challenge, John Ross Galbraith shot a two-under 69 and Old Conna's Neil O'Briain a 70 as the Czech Republic's Stanislav Matus fired a 10-under 61 to lead by two shots from Australia's Dimitrios Papadatos, Sweden's Sebastian Soderberg, England's Tom Lewis and English amateur Thomas Sloman.