Tiger Woods came up short in his bid for a magical 59, but still opened up a commanding lead in his quest for an incredible eighth WGC-Bridgestone Invitational title.
Nine under par after 13 holes of the par 70 Firestone Country Club, Woods needed to play the last five holes in two under to record the first 59 in European Tour history.
However, after scrambling a par on the 14th, a good chance for birdie from nine feet went begging on the 15th and the World Number One's chance to break the 60 barrier effectively disappeared when he missed from six feet on the 17th.
A wild drive on the 18th looked set to lead to a disappointing closing bogey, but Woods holed from 25 feet for par to card a 61, equalling the lowest round of his career and setting him up for a 79th US PGA Tour title, three behind Sam Snead's all-time record of 82.
At 13 under par Woods held a seven shot lead over defending champion Keegan Bradley and England's Chris Wood, who were both round in 68, with Open Championship runner-up Henrik Stenson and American Bill Haas another stroke back.
"I had it going today, it was a nice start," Woods said. "Four under through three is always nice and I let the round build from there. I made a couple of key putts for par and kept the momentum going."
Asked about shooting 59, Woods added: "I certainly could have done it, I've done it before (in practice at his home course of Isleworth).
"I felt pretty relaxed with it. If I hadn't shot 59 before it would have been a different story. I was only nine under at the time, when I did it I was 13 under. I figured I have been in these positions before where I have gone low so it was not out of the realm of being uncomfortable."
Two shots off the pace after an opening 66, Woods holed from three feet for a birdie at the first, 20 feet for eagle at the second and 12 feet for birdie at the third to vault into the lead.
He got up and down for par on the next two holes - the latter from a greenside bunker - and then made a more adventurous par on the sixth after his pulled drive ended up at the base of a tree.
From there he could only chip out across the fairway alongside playing partner Hideki Matsuyama's tee shot, but after hitting his third shot into 25 feet the 14-time Major winner holed for an unlikely four.
A superb tee shot to within three feet of the pin on the seventh set up another birdie from the seventh one-putt of the round, but that run finally came to an end with a two-putt par on the eighth.
A birdie putt from 15 feet on the ninth narrowly missed but Woods was still out in 30 and not about to slow down either, holing from seven feet on the tenth, five feet on the 11th and 20 feet on the 12th for a hat-trick of birdies to leave the field trailing in his wake.
Woods made the most of a stroke of good luck on the 13th, hitting his approach to 15 feet and making the birdie putt after his drive had bounced off a tree and back into the fairway.
Another bad drive on the next was not so fortunate, although Woods did have a shot through the trees and was able to find the back of the green, from where he chipped to six feet and holed for par.
An excellent chance for yet another birdie went begging on the 15th and a poor approach to the par five 16th led to a third par in succession, but the 59 looked back on the cards when Woods conjured a superb shot from the rough on the 17th.
However, the birdie putt from six feet slipped past the hole and in the end Woods had to scramble a par on the last to avoid an undeserved low-key finish.
Wood, making his debut in the event courtesy of winning the Commercial Bank Qatar Masters in January, carded four birdies and two bogeys in his 68.
The second of those dropped shots came on the 18th and cost him outright second, but with play switching to threesomes tomorrow due to forecast bad weather, the 25 year old will still be in the final group with Woods and Bradley.