Maverick McNealy, a Northern California native and Stanford product, moved to the top of the Fortinet Championship leaderboard after an up-and-down round Friday in Napa, Calif.
McNealy shot an 8-under-par 64 to take a two-stroke lead. He sits at 12-under 132 through two rounds.
Beau Hossler also carded a 64 at Silverado Resort and Spa's North Course, and he shares second place with Chile's Mito Pereira, who produced a 67 on Friday. Both are at 10 under.
Will Zalatoris (67 on Friday), Bronson Burgoon (67) and Troy Merritt (68) are tied for fourth place at 9 under. Matt Kuchar (66), Scotland's Russell Knox (67) and Harold Varner III (68) are at 8 under, tied for seventh.
World No. 1 Jon Rahm of Spain can focus preparing for the Ryder Cup next week after missing the cut. He shot a 1-under 71 on Friday to finish at 1-under 143 through two rounds, two strokes off making it to the weekend.
Reigning Masters champion Hideki Matsuyama of Japan logged his second consecutive 69 and is tied for 17th at 6 under. Matsuyama is one shot ahead of Phil Mickelson, who shot a 69 on Friday and is tied for 24th.
McNealy, 25, is still in search of his first PGA Tour win in four years since turning pro after a stellar collegiate career. He best finish came earlier this year at another Northern California event, the ATT Pebble Beach Pro-Am.
On Friday, starting on the back nine, McNealy birdied three of the first four holes and was 5 under par on the day at the turn. He then bogeyed Nos. 10, 11 and 12 and before following immediately with four consecutive birdies, capped by holing out from a greenside bunker. Following a par at No. 8, he closed by chipping in for eagle on the par-5 ninth hole.
"It was a roller-coaster day," McNealy said. "The (first) nine I played just about flawless golf, hit it where I wanted to. Then I got to the first hole and funny lie in the right rough and dumped it in the bunker shot and shanked the bunker shot, got up and down for bogey and then bogeyed the next two. I was kind of going, 'Oh, man, this is going the wrong way quick.'
"The fourth hole was kind of a pivotal hole for me. My caddie, he walks the entire golf course every week before I even play it and he gets all of his numbers. He got me a really good number to cover on that bunker on that wedge shot, hit a great wedge in there to eight feet and made birdie and that kind of turned things around and finished strong."
Hossler turned in a bogey-free round while Pereira had five birdies, two bogeys and an eagle on the par-5 fifth hole.
--Field Level Media