Webb Simpson braved the sweltering heat and gusty winds to take a two-shot lead at the Dean & DeLuca Invitational on Saturday.
Having started the day with a share of the lead, Simpson quickly burst out of the pack with birdies on his first two holes.
He bogeyed the par-three eighth hole, but quickly birdied 10 and 11 to ultimately shoot a three-under 67.
Simpson, who won the 2012 U.S. Open but last tasted success on the PGA Tour at the 2013 Shriners Hospitals for Children Open, sits at nine under.
Paul Casey and Danny Lee both birdied the par-four 18th hole Saturday to get within two shots of Simpson's lead.
Casey finished round three with four birdies and two bogeys while shooting a two-under 68 in tough scoring conditions.
Lee, who had fallen all the way down to 125th in the world rankings after ending last year in the top 70, finally found his form last week at the AT&T Byron Nelson, where he was tied for fifth.
Stewart Cink and Kevin Kisner are tied for fourth at six under.
Jon Rahm survived an up-and-down round to shoot an even-par 70. He is tied for sixth at five under with Sean O'Hair.
Rahm had five birdies and five bogeys on his scorecard in round three.
Last year's PGA Tour Rookie of the Year Emiliano Grillo shot a 65 - the low round of the day - to get into the top 10 at four under. He is tied for eighth will Bill Haas, Jordan Spieth, Sergio Garcia and Scott Piercy at the edge of contention.