Americans Keegan Bradley and Sam Burns shared a slender lead after the third round of the Valspar Championship at Innisbrook's Copperhead course in Florida.
While England's Tom Lewis slipped down the leaderboard, Bradley and Burns carded two-under 69s to be 14-under for the tournament, a shot clear of compatriot Max Homa after his 66.
Three shots further back were a group of four players including American Ted Potter - who had the round of the day with an eight-under 63 - and Mexico's Abraham Ancer, who took a 66.
Lewis was five shots off the lead at the halfway mark but struggled with a three-over 74 on Saturday. The 30-year-old turned at one-under for the day after two birdies and a bogey, but endured a horror inward nine of five bogeys offset by one birdie at the 14th.
This left him at four-under for the tournament, in a group sharing 28th spot along with England's Ian Poulter, who shot a 69, and Scotland's Russell Knox, who took a second successive 70.
Paul Casey's bid for a third straight win at the tournament also met with disappointment, as the Englishman shot a one-over 72 to sit 12 shots off the pace.