Sam Burns claimed a two-stroke lead at the halfway stage of the Safeway Open, where former world number one Jordan Spieth missed the cut.
Burns was a shot adrift of overnight leader Russell Knox heading into the second round, but the American carded a seven-under-par 65 to move to the top of the leaderboard on Friday.
At the Silverado Country Club in Napa, California, where the 2020-21 PGA Tour season is getting underway, Burns was almost flawless following nine birdies and a double bogey.
Burns is 15 under through 36 holes, ahead of fellow American Harry Higgs – who catapulted himself into contention with a stunning 10-under-par 62.
Higgs was bogey-free with a final-hole albatross and seven birdies as he climbed 34 positions into outright second spot.
Knox (69), Cameron Percy (68) and D.J. Trahan (65) are three shots behind Burns heading into Saturday's third round.
Five-time major champion Phil Mickelson posted a second-round 67 to be tied for 34th at six under.
Spieth's woes continued after he failed to qualify for the weekend following back-to-back rounds in the 70s.
Without a top-10 finish since February's AT&T Pebble Beach Pro-Am and winless since the 2017 Open Championship, Spieth shot a 70 to reach one under, well adrift of the five-under cut-off point.
Former Masters champion Sergio Garcia (69) also missed the cut.