US rookie Jake Knapp fires 63 to grab lead at PGA Tour Mexico Open
The American birdied seven of the first nine holes for a course-record seven-under 28 on the front side at Vidanta in Puerto Vallarta.
A birdie-birdie finish gave Knapp 11 birdies against three bogeys on the day to match the 54-hole tournament scoring record of 19-under 194 set last year by winner Tony Finau.
That was good enough for a four-stroke lead over Finland's Sami Valimaki, another PGA Tour rookie in only his 11th start on the circuit, with Canada's Ben Silverman, Sweden's Henrik Norlander and American Chan Kim sharing third on 201, seven strokes adrift.
World number 101 Knapp, who shared the lead on 11-under when the day began, birdied six of the first seven holes, reeling off four in a row from the fourth, and birdied the ninth to seize command, telling himself to stay focused as the birdies fell.
"Just keep it going, stick to the process, do what we've been doing," Knapp said. "Kept saying I've been hitting the ball well, just keep giving myself opportunities and get some putts to drop and was able to do that."
Knapp, who produced his best PGA finish with a share of third earlier this month at Riviera, has won three times on a Canadian developmental tour and will rely on years of past efforts to cope with Sunday pressure in the biggest round of his career.
"I've been playing professional golf for a while and had plenty of good stuff and bad stuff," he said.
"What happened at (Riviera), I have that to lean back on, and some experiences on the Korn Ferry and Canadian tours and all that, so that will all be a part."
Knapp opened with back-to-back birdies, hitting his approach at the first from the left rough to just inside three feet of the hole, then blasting his approach to four feet at the second.
Knapp sank a birdie putt at the fourth from just inside 17 feet, followed with a 24-foot birdie putt at the par-3 fifth, another from just outside five feet at the par-5 sixth and made a five-foot birdie putt at the par-4 seventh after driving onto the green.
At the par-3 ninth, Knapp landed his tee shot four feet from the hole and tapped in to set the nine-hole tournament record and lead by three at the turn.
Bogey bounce backs
At the 10th, Knapp went way left off the tee, needed a penalty drop and sank a putt from just inside 10 feet to salvage bogey.
Knapp responded with an 11-foot birdie putts at the par-3 11th and par-5 12th.
Knapp missed a par putt from just inside nine feet and made bogey at the par-5 14th, then missed the green with his approach at the par-4 16th and missed a 14-foot par putt for another bogey.
Again Knapp answered, sinking a 14-foot birdie putt at the par-3 17th and two-putting from 35 feet for a birdie at the par-5 18th to close his spectacular round.
Valimaki, a two-time DP World Tour winner, closed with a birdie to shoot 67 to join Knapp in Sunday's final group.
A pack sharing sixth on 202 included England's Matt Wallace, Scotland's Robert MacIntyre, American Justin Lower and South African Erik van Rooyen.