Australian Min Woo Lee birdied seven of the first 14 holes in firing a seven-under par 63 to seize a four-stroke lead after Saturday's third round of the PGA Houston Open.
The 26-year-old from Perth finished one off the Memorial Park course record to stand on 17-under 193, a 54-hole tournament record.
"Just some solid golf," Lee said. "Been playing really good the last few days. Just keep my head down."
Argentina's Alejandro Tosti shot 65 to grab second on 197 with top-ranked Scottie Scheffler, fellow American Ryan Gerard and New Zealand's Ryan Fox on 198.
"I've learned from past experiences and obviously playing with Scottie the past few years, in the final group in a couple tournaments," Lee said.
Lee, with his first 54-hole lead in a PGA event, seeks his first PGA title after three wins on the European Tour.
"Hopefully tomorrow is another good day," Lee said. "Similar golf (to win). Just got to play pretty steady off the tee. A couple shaky drives at the end but kind of regrouped and made it happen. Just keeping my head down and one shot at a time."
While Lee, Fox, Tosti and Gerard each seek a breakthrough first PGA triumph, Scheffler won nine titles worldwide last year, including his second Masters and Paris Olympic gold, and matched the course record with a 62 on Friday.
Scheffler was bogey-free for the week until he followed a birdie at the par-5 third with a bogey after missing the green with his approach at the fourth.
Scheffler birdied the par-5 eighth and answered a bogey at 13 with a birdie at the par-5 16th but the 36-hole leader only managed a 69.
"Yesterday I holed a bunch of putts, today I feel like I couldn't get the ball to go in the hole," Scheffler said. "Feel like I hit a lot of good putts.
"There's not really much you can do different out there. Try to shoot as low as possible today and I'm going to try to do the same thing tomorrow."
Lee sank a six-foot birdie putt at the par-5 third and chipped in for birdie from 34 feet at the par-4 sixth to grab the lead at 12-under.
Lee dropped his approach inches from the hole at the par-5 eighth and par-3 ninth to set up tap-in birdies on both holes and sank a birdie putt from just inside 12 feet at the 10th for his third consecutive birdie to reach 15-under and stretch his lead to three strokes.
World number 55 Lee birdied the par-4 12th after landing his approach inside five feet and when Scheffler made bogey at the 13th, the Aussie had a five-stroke edge.
Lee sank his seventh birdie in 14 holes, a seven-footer at 14, and parred his way to the clubhouse.
MCILROY 'PLAYED OK'
World No 2 Rory McIlroy, who birdied three of the last four holes Friday to make the cut, fired a 65 to reach 201, eight strokes adrift.
The Northern Ireland star, who would complete a career Grand Slam by winning next month's Masters, began on the back nine and holed out an eagle chip from just inside 54 feet at the par-5 eighth to highlight a bogey-free round.
"I played OK," McIlroy said. "It was nice to get out there and play decent. Certainly didn't have my best, but shot a decent round and hopefully another good one tomorrow."
American Davis Thompson birdied seven of the first 10 holes on his way to a 64, matching his best PGA round to stand on 200.
"It was a good day," Thompson said. "It gives me confidence knowing I'm playing well. Just got to go do the same thing tomorrow, give myself a lot of good looks and make a few of them."