Steve Stricker opened up a five-shot lead at the midway stage of the Tournament of Champions with a stunning 10-under-par 63 in his second round in Hawaii.
The Wisconsin-born 44-year-old, who started with a 68 on Friday, picked up eight birdies and an eagle in a flawless round on the Plantation Course at Kapalua to move to 15 under par.
Webb Simpson was his nearest challenger after a 68, with fellow American Kevin Na in third place - a further stroke back - after an eagle-eagle finish helped him card a 64.
Defending champion and first-round leader Jonathan Byrd signed for a two-under 71 and was seven shots off the pace in a tie for fourth alongside Scotland's Martin Laird (70).
Stricker was delighted with his round but was not getting carried away.
"It was a special day," he said. "When you can shoot 10 under, a lot of good things have to happen. I gave myself a lot of opportunities. I made a lot of putts. I just played consistent, really never got into any trouble.
"It was just a good, solid round of golf. We're only halfway, through, so I've got still a lot of work left to do - I realise that.
"So I've just got to come out tomorrow with the same mentality that I've had every other day, and that's just to take one shot at a time and keep plugging away."
Asked if Ernie Els' 2003 tournament mark of 31 under par had entered his thoughts, he replied: "It doesn't enter my mind, and I really hate putting numbers on anything.
"I just go out and take what it gives me, really, if I'm feeling good, if I'm aggressive and can take advantage of some holes out there.
"But I really just get into the situation at hand and go from there, and that's what I did well today. I ran with it. I felt good. I started making some birdies and I was patient when I wasn't making some."