San Francisco - Bryson DeChambeau fired eight birdies in an eight-under par 64 on Friday to seize a two-shot lead over fellow American Nick Watney at the PGA Tour's Safeway Open in Napa, California.
DeChambeau, seeking sixth Tour title and his first since he won in Las Vegas last November, was buoyed by a couple of birdie bombs, including a 36-footer at the sixth hole and a 23-foot birdie putt at 14 - where he was in a fairway bunker off the tee.
His 21-foot eagle putt at 18 came up just short, but he tapped in for a final birdie and a 36-hole total of 132 on the Silverado course.
"I made a couple of good putts, that was obviously awesome," world No 11 DeChambeau said after his second straight bogey-free round.
"I struck it better today. Honestly the key to my play these last couple of days was my wedge play," added DeChambeau, who was delighted with the performance of new wedges with stiffer graphite shafts.
Watney had eight birdies and a bogey in his seven-under 65 and was alone in second on 134, one stroke in front of a group of five players.
World number six Justin Thomas headlined the group on 135 after a 64 that featured nine birdies and just one bogey. He was joined by Canadian Nick Taylor, who carded a 66, South African Dylan Frittelli who posted a 65 and Americans Adam Long and Cameron Champ, who both shot 68.
Thomas, who closed fast after a shaky start on Thursday, kept up the good work to put himself in contention heading into the weekend of his first start of the season.
"I know that you can go low out here," he said.
"It's a course that it's very short and the ball goes quite a long way with how firm it is.
"But because of how firm it is, you have to get it in the fairway and really have the correct angles into the greens, and I felt like I did a pretty good job of that today."
Australian Adam Scott and American Andrew Landry, who shared the overnight lead, both slipped back, Scott carding a one-over 73 that left him six adrift and Landry with a 74.
Former NFL star Tony Romo, whose chances of making a first cut at a PGA Tour event looked promising after his first-round 70, plummeted down the leaderboard with a six-over 78 that left him four-over for the week.
The 39-year-old American, who played 14 seasons for the Dallas Cowboys, was playing on a sponsor exemption for the fourth time in a PGA event.
Five-time major-winner Phil Mickelson, hoping for strong enough showings in the tour's early 2019/20 tournaments to become a captain's pick for a 12th straight Presidents Cup team, also missed the cut, which fell at two-under, by two strokes.
Leading second-round scores on Friday in the PGA Tour's Safeway Open in Napa, California (USA unless noted, par 72):
132 - Bryson DeChambeau 68-64
134 - Nick Watney 69-65
135 - Nick Taylor (CAN) 69-66, Dylan Frittelli (RSA) 70-65, Adam Long 67-68, Justin Thomas 71-64, Cameron Champ 67-68
136 - Collin Morikawa 72-64, John Oda 70-66
137 - Brian Gay 70-67, Robby Shelton 70-67, Chez Reavie 69-68, Francesco Molinari (ITA) 66-71, Zhang Xinjun (CHN) 69-68
138 - Talor Gooch 69-69, Adam Hadwin (CAN) 68-70, Jim Furyk 71-67, Harris English 70-68, Charles Howell 73-65, Sebastian Munoz (COL) 71-67, Adam Scott (AUS) 65-73