San Francisco - Dustin Johnson rolled in a 10-foot birdie putt at the 18th on Saturday to grab a share of the Pebble Beach National Pro-Am lead with Ted Potter Jr., who flirted with a 59.
World number one Johnson fired an eagle and four birdies in his two-under par 70 at Pebble Beach Golf Links, one of three tournaments in use for the first three rounds of the PGA Tour event.
Potter was chasing history at the par-71 Monterey Peninsula layout, where he teed off on 10 and played his first seven holes in seven under par with five birdies and an eagle.
Potter added four more birdies after the turn to seize the solo lead and take his total for the round to 11-under. He needed one more birdie to post just the 10th sub-60 round ever on the US PGA Tour.
But he closed with back-to-back bogeys to settle for a nine-under 62 and a share of the lead with Johnson on 14-under 201.
Potter's only prior US PGA Tour win came at the Greenbrier Classic back in 2012. In 2014 he broke his right ankle in a freak accident stepping off a curb. The injury required surgery and he has battled back since, earning his PGA Tour card via the Web.com Tour last season.
On Sunday he'll be in the hunt along with Johnson -- who opened 2018 with a dominant victory in the Tournament of Champions last month -- and former world number one Jason Day of Australia.
Day, winner at Torrey Pines two weeks ago, had six birdies in a three-under par 69 at Pebble Beach for a 12-under total of 203.
He was tied with Troy Merritt who signed for a 69 at Monterrey Peninsula.
World number two Jon Rahm of Spain fired a 70 at the par-72 Spyglass Hill to head a group on 204 that also included Steve Stricker (70) and Patrick Rodgers (69).
Johnson was quick out of the blocks with an eagle at the par-five second hole. After a bogey at the third, he rolled in birdies at the fourth, sixth and seventh -- where he drained a 28-footer to get to 16-under for the tournament.
But things got tougher coming in, with bogeys at 10, 12 and 17 before he regained a share of the lead with his closing birdie.
"I got off to a really good start," Johnson said. "Even played pretty well on the back nine, had a lot of good looks at some nice birdies and hit good putts that just didn't go in.
"The couple of bogeys that I made were kind of just poor. The wind was a little bit tricky and I just got on the wrong side of the holes.
"All in all," he added, "I feel good about the game. I've got a lot of confidence going into tomorrow."
Putting troubles derailed Rory McIlroy's first Pebble Beach National Pro-Am bid as the Northern Ireland star failed to make the cut.
With five birdies and five bogeys, McIlroy's even par 72 at Pebble Beach left him one-under for the tournament and outside the cutline by two strokes.
"I hit some really good shots," McIlroy said. "I just needed a few putts to fall."