Webb Simpson is one of four players in a tie for the lead at the RBC Heritage after the third round on Hilton Head Island.
Former U.S. Open champion Simpson is level at 15 under par through 54 holes alongside Tyrrell Hatton, Abraham Ancer and Ryan Palmer.
Simpson, the 2013 RBC Heritage runner-up, held the outright lead overnight but could only manage a three-under 68 in a round that contained four birdies and one bogey.
His fellow American Palmer shot 66, while Mexican Ancer posted a third-round 65 to join Simpson at the front of the PGA Tour event.
Englishman Hatton also surged into contention and shares the lead after following up a disappointing opening round of 71 with scores of 64 and 63.
His eight-under effort on Saturday was tied for the best of the day along with five other players.
Similarly to last week's Charles Schwab Challenge, the top of the leaderboard is hugely congested going into the final day.
There are 17 players sitting within three strokes of the four leaders.
Daniel Berger (63) – the winner at Colonial – matched Hatton's total and is one of three men one shot behind on 14 under along with Joel Dahmen (63) and Carlos Ortiz (63).
Ian Poulter (67) – who held a share of the lead after round one – is two strokes off the pace along with Sergio Garcia (65) and a further six competitors.
Four-time major champion Brooks Koepka (68) and former world number one Dustin Johnson (67) remain in contention at 12 under, as does Bryson DeChambeau despite struggling in a third round of 70.
Despite a five-under-par 66, world number one Rory McIlroy has work to do at 10 under heading into the final round.
McIlroy sits five shots behind Simpson, Hatton, Ancer and Palmer in a tie for 28th after holing six birdies and a bogey – eight strokes better off than Jordan Spieth, who struggled in a four-over-par 75.
Meanwhile, the field was a combined 223-under par, the most of any round in this tournament's history, surpassing 178 under in 2015.