Austin Cook moved a step closer to the RSM Classic title as he extended his lead to three strokes after the third and penultimate round.
American rookie Cook carded a four-under-par 66 to remain top of the leaderboard at the Sea Island Golf Club on Saturday.
Seeking his first PGA Tour trophy, Cook teed off with a one-shot lead on the weekend and he improved that buffer thanks to a bogey-free front nine which included four birdies.
The 26-year-old - who recovered from his first bogey of the tournament at the 14th - is 18 under through 54 holes, ahead of countryman and 2013 champion Chris Kirk.
"Bouncing back from any bogey with a birdie is nice and helps get the number right back. Being my only bogey of the week so far, it was really nice to be able to get that back on the next hole," said Cook.
"Going into tomorrow [Sunday] with a three-shot lead instead of a two-shot lead I think is crucial."
Kirk recorded seven birdies for a six-under-par 64 to earn outright second.
Brian Gay (69) is 14 under, while J.J. Spaun is a shot further back following his third-round 62.