Phil Mickelson flirted with a 59 on Friday, but eventually fell short en route to an 8-under 63 to grab a share of the lead at the end of the first round of the Deutsche Bank Championship.
Brian Davis, who has missed his last four cuts, also shot 63 to meet the reigning British Open winner atop the leaderboard at TPC Boston.
Kevin Stadler sits alone in third place at 7-under 64, while Hunter Mahan, Sergio Garcia and Roberto Castro are tied for fourth at 6-under.
PGA Championship winner Jason Dufner highlights a large group of players occupying seventh place at 5-under 66.
Among those joining Dufner are Steve Stricker, Matt Kuchar, Ian Poulter and Lee Westwood.
Defending champion Rory McIroy carded an up-and-down 1-under 70 to sit in a tie for 56th place.
Mickelson's quest for 59 started with an outward 28 that gave him early control of the tournament.
The surge started with a 19-foot birdie at the 10th (his first) that he followed with a 28-foot birdie effort at the 11th.
After parring his next two holes, Mickelson rolled in five straight birdies from the 14th to make the turn at 7-under. Only two of those five birdie putts came from inside 10 feet, as the left-hander converted putts of 18, 15 and 11 feet during that stretch.
"I putted really well. There were a couple that didn't go that had just as good a chance to go as the ones that did, and that's the sign that you're putting well, when the ones that you are missing are catching lips, and I had three or four that did," said Mickelson. "I'm rolling the ball well."
A bogey at the first halted his birdie streak when he failed to get up and down from a greenside bunker, but he bounced right back by sticking his second shot at the par-5 second to two feet from the hole and kicked in that short eagle to move to 8-under.
"It's really fun. You actually feel like there's less pressure," Mickelson said of his front nine. "I feel like I didn't have to knock it stiff because I was making putts. I just had to get it on the green to give myself a chance and a lot of the ones went in."
Mickelson parred his next five holes to end his hopes of shooting 59 and following another lengthy birdie putt at the eighth, an errant tee shot at the last settled about waist high in a bush.
He opted to smack the ball out instead of taking an unplayable lie, and eventually 2-putted for bogey to head into the clubhouse with the lead at 8- under.
"After I did not birdie four and missed the (putt) on three from about 15 to 18 feet, I stopped thinking 59 and was trying to get one or two more (birdies) coming in and shoot something in the low 60s," stated Mickelson.
Davis' 63 was less eventful as he went out with one of the last groups of the day and opened his round with an 8-foot birdie putt at the 10th.
He parred his next five holes before converting a trio of birdies from the 16th to make the turn at 4-under.
Davis rolled in a putt from off the green at the third and made it two straight birdies at the fourth to pull within two strokes of Mickelson, and was able to grab a share of the lead by capping consecutive birdies at the 17th and 18th with a 24-foot birdie putt at the last.
"The FedEx is great drama," Davis said. "For us guys a lot of volatility. You know you have to play well. I missed a couple of shots last week, you can make some big jumps, and get points in the playoffs. Coming today, I played great."
Stadler also started on the back nine and countered a bogey at the 12th with consecutive birdies at the 14th and 15th.
He added another birdie at the 18th to make the turn at 2-under, and later closed with five birdies over his final six holes to move within a shot of Mickelson and Davis.
NOTES: Mickelson's 28 tied a career-low, 9-hole score and the back nine scoring record at TPC Boston ... Davis' 63 tied his best career round on the PGA Tour ... McIlroy is trying to join Vijay Singh (2004 and 2008) as the only multiple winners of the event ... Tiger Woods (2006) and Steve Stricker (2009) are the only first-round leaders/co-leaders at the Deutsche Bank Championship to carry that lead on to victory.