Brendan Steele shot a three-under-par 69 to retain the lead after the third round of the Frys.com Open on Saturday, while world number three Rory McIlroy endured another mediocre day on the greens in northern California to slide out of contention.
Steele, on 14-under-par, holds a one-shot advantage over fellow Americans Andrew Loupe (63) and Kevin Na (64), with world number seven Justin Rose (68) among a group of eight two shots back on a crowded leaderboard at the Silverado Resort.
"Today was a test of patience,” said Rose, the 2013 U.S. Open champion, after a bogey-free round.
"I think I did the bare minimum required to keep believing and give myself a good chance tomorrow. It’s going to take something pretty good to pull through and win.”
McIlroy, who carded a 71 to sit eight shots off the lead, had a narrow escape when he was almost struck by Argentine Emiliano Grillo's tee shot.
The Northern Irishman had just played a chip shot from next to the green at the driveable par-four 17th when Grillo's drive landed only a couple of feet from the surprised McIlroy, who clearly received no warning.
Steele, seeking a second PGA Tour win, started the day with a two-shot lead but could not extend his advantage despite the benign conditions.
"I'm really happy with the state of my game all the way through the bag," the 32-year-old, who was raised in a small town in the southern California mountains, told PGA Tour Radio.
Loupe scored early and late en route to the best round of the day and a share of the course record in the opening event of the 2015-16 PGA Tour season.
He birdied the first five and the last four holes to move within sight of his maiden tour victory. He has never finished better than fourth on the Tour.
"Getting off to a start like that ... it was fun to just run out there like that and then finish well," Loupe said. "Fabulous day, had a great time."
South Korean-born Na is seeking his second tour win after several near-misses since his lone triumph in 2011.
He jumped into contention with a six-foot eagle at the par-five 16th, and added a tap-in birdie at the last.
"The course was there for the taking a little bit and I took advantage of it," Na said.