Miami - Austin Cook will take a three-shot lead into the final round of the RSM Classic after firing a four-under-par 66 at Sea Island, Georgia, on Saturday.
The 26-year-old PGA Tour rookie, who produced a scintillating 62 on Friday, enjoyed another solid outing on the par-70 Seaside course to move to 18 under.
Cook did most of the damage over the front nine, opening with back-to-back birdies on his first two holes before grabbing two more at the seventh and ninth to be four under at the turn.
He dropped a shot on the par-four 14th when he three-putted but recovered with a birdie on the par-five 15th, rolling a 38-foot putt to four feet for a tap-in.
Cook leads by three from Chris Kirk, who took sole possession of second place with a six-under-par 64, giving him a 15-under-par 54-hole aggregate of 197.
Kirk recorded seven birdies with one bogey. His final birdie of the day came on the 17th, when he rolled in a 29-foot putt to get down in two.
Brian Gay is one shot back on 14 under after a one-under-par 69.
The round of the day came from J.J. Spaun, who moved into contention with an eight-under-par 62.
Spaun, 27, produced some immaculate iron play to carve out a series of birdie opportunities which his flawless putter duly converted.
His bogey-free round included eight birdies, including four in a row on the front nine which put him five under at the turn.
Spaun, who has never won on the PGA Tour, then picked up three more birdies on the back nine to finish the day at 13 under, five off the lead.
"I just kind of played stress-free golf out there," Spaun said. "Overall pretty pleased with how I played today.
"My goal all year is just to be in contention with 18 holes to play. So to be near that leading group on the last day is kind of where I want to be, so I'm not complaining."
Kevin Kisner is one shot back on 12 under after a five-under-par 65, while Andrew Landry and Vaughn Taylor are tied in sixth at 11 under.
Leading scores after Saturday's third round of the US PGA RSM Classic on the par-70 Seaside course at Sea Island, Georgia (USA unless noted):
194 - Austin Cook 66-62-66
197 - Chris Kirk 63-70-64
198 - Brian Gay 65-64-69
199 - J.J. Spaun 67-70-62
200 - Kevin Kisner 67-68-65
201 - Andrew Landry 70-64-67, Vaughn Taylor 67-66-68
202 - Aaron Wise 68-69-65, Zach Johnson 70-68-64, Tyler Duncan 68-70-64, Brian Stuard 67-68-67, Brice Garnett 65-69-68
203 - Stephan Jaeger (GER) 68-69-66, Brian Harman 69-68-66, Ted Potter Jr 68-68-67, William McGirt 70-68-65, Johnson Wagner 67-69-67, Michael Thompson 68-68-67, Bud Cauley 72-63-68, Kelly Kraft 70-65-68, Blayne Barber 67-67-69, Kang Sung (KOR) 66-69-68, Ben Silverman (CAN) 67-67-69