John Mallinger will take a two-shot lead into the final round of the Frys.com Open after a one-under 70 in Saturday's penultimate round, while Australian Nick O'Hern dropped off the pace.
The American, who led by four strokes at the halfway mark, hit three birdies and two bogeys to move to 15-under and retain his position atop of the leaderboard at CordeValle Golf Club.
O'Hern, the opening-day leader, endured a difficult end to the third round as he hit three bogeys on his final five holes.
O'Hern (71) slipped six shots adrift of leader Mallinger and is placed at nine-under alongside Ryder Cup winner Nicolas Colsaerts and five others.
Fellow Australians Nathan Green (68), Steven Bowditch (71) and Matt Jones (70) are tied for 28th, while Rod Pampling (69) and Matthew Goggin (69) are further back.
Swede Jonas Blixt was one of the day's best performers with a five-under 66 to climb to 13-under.
Still searching for his maiden PGA title, Blixt sunk five birdies on the final nine holes to move one shot clear of American pair Charles Howell III and Jason Kokrak.
Howell III carded a five-under 66, while Kokrak recorded a four-under 67 as the two Americans finished the day at 12-under for the tournament.
Fijian Vijay Singh and Brazil's Alexandre Rocha carded matching rounds of 66 to climb 10 positions into a tie for fifth at 11-under.
Singh, a former world number one, closed the day with a hole-in-one at the 17th.
Venezuelan Jhonattan Vegas, who began the day in second place, had to settle for a share of seventh after a difficult session on Saturday.
Vegas fell five shots off the pace after hitting an even-par 71 and is now tied for seventh with Scotland's Russel Knox (65), New Zealander Danny Lee (67), Englishman Greg Owen (68) and American Scott Dunlap (70).