American Wyndham Clark shot a course record 60 to take the lead heading into the final round of the AT&T Pebble Beach Pro Am.
The US Open champion made five putts of at least 25 feet in his 12-under-par round with two eagles, nine birdies and one bogey, eclipsing the previous record of 62.
Clark, who had a lengthy eagle putt at the last to break 60, said he had a “really good feel on the greens”.
He said: “I was just, ‘See ball, hit ball, try to hit it where I wanted to’.
“So in my mind I was like, ‘All right, let’s just get us to where we’re putting,’ because the hole seemed like a bucket today.”
Clark’s round does count as a course record on the PGA Tour, despite the players being able to clean and place balls on the fairways.
Sweden’s Ludvig Aberg continued his strong tournament with a five-under-par 67 to sit one shot off the lead, with France’s Matthieu Pavon a further shot behind as he chases a second successive victory on tour.
Justin Rose shot a 66 to move to 11-under par – six off the lead – but Rory McIlroy was a further nine strokes adrift after a 69.
The final day’s play could be determined by weather with strong winds and rain threatening to delay or cut short play.