San Francisco - American Tyler Duncan fired a six-under par 66 to take a one-shot lead at the halfway stage of the PGA Tour's Safeway Classic on Friday.
Duncan had an erratic second round, but an eagle on the ninth helped offset a string of three consecutive bogeys at the Silverado Resort and Spa in Napa, California.
Duncan, who began the day tied for first, had a two-day total of 13-under 131, a stroke ahead of defending champion Brendan Steele, who shot a 67.
The tournament is the opener of the 2017-18 PGA Tour schedule.
Duncan began the day at the 10th. He had three birdies on his front nine, but then had three straight bogeys coming in, at the third, fourth and fifth.
He righted himself with birdies at seven and eight before an eagle at his final hole, the par-five ninth.
Steele had a bogey in his round, but he offset that with six birdies.
Chesson Hadley shot the best round of the day, firing an 11-under 61 that left him alone in third place on 133.
Hadley, who had lost his PGA Tour card at the end of the 2016 season, carded 10 birdies, a bogey and an eagle to put himself in the hunt going into the third round.
Zac Blair with a 66 and Tony Finau after a 65 were tied for fourth, two strokes behind Hadley on 135.
It was a further stroke back to Graham DeLaet of Canada and Brian Davis of England, DeLaet carding a 67 and Davis a 66 for 136.
Five-time major winner Phil Mickelson signed for a 69 and was tied for 15th on 138.
Leading second round scores on Friday in the PGA Tour Safeway Open at Napa, California (USA unless noted):
131 - Tyler Duncan 65-66
132 - Brendan Steele 65-67
133 - Chesson Hadley 72-61,
135 - Zac Blair 69-66, Tony Finau 70-65
136 - Graham DeLaet (CAN) 69-67, Brian Davis (ENG) 70-66
137 - Chez Reavie 67-70, Bill Haas 72-65, Martin Flores 70-67,
Emiliano Grillo (ARG) 67-70, Harold Varner 69-68, Kevin Streelman 69-68,
Andrew Putnam 71-66