Sang-Moon Bae has carded a third-round 65 to take a four-shot lead into the final day of the Frys.com Open at Silverado in Napa.
The South Korean sank five successive birdies in an impressive front-nine showing before that run came to an end with a bogey on the seventh.
Another bogey on 13 followed, but Bae produced a rousing finish by picking up two birdies and an eagle in the final four holes to end day three on 16-under, four strokes clear of Zachary Blair.
Blair failed to follow up an impressive 66 on day two by shooting a third-round 69, with two bogeys on 12 and 13 partially cancelling out his five birdies.
Matt Kuchar, meanwhile, produced a bogey-free round of 66 to sit five shots off the pace heading into the fourth and final day in California.