Los Angeles - Wyndham Clark fired 10 birdies in a 10-under par 61 on Thursday to grab a two-shot lead over fellow American Billy Horschel in the PGA Tour's Phoenix Open.
Amid the always raucous crowds at TPC Scottsdale, Clark teed off on 10 and rolled in a 20-foot birdie putt at the 12th.
After another birdie at 13 he picked up three in a row at 15, 16 and 17.
He strung another three together at the first, second and third - where he blasted out of a greenside bunker to five feet and made the putt - and birdied seven and eight for good measure.
Clark seized the solo lead with a birdie at the par-three seventh, where he stuck his tee shot three feet from the pin, and made it a two-shot advantage with an 11-foot birdie putt at eight.
"I hit a lot of fairways and I just gave myself a lot of looks and the putter was hot," Clark said.
A red-hot putter fuelled Horschel, who had six birdies and an eagle in his eight-under 63.
Horschel rolled in two birdie putts from outside 25 feet and one from 41 feet, along with a par-saving 45 footer.
His eagle at the par-five third hole didn't need that kind of putting aplomb after he landed his second shot five feet from the hole.
JB Holmes used an eagle hole-in-one at the par-three third and eight birdies to overcome an early double-bogey and a bogey, his seven-under 64 putting him alone in third.
He stormed home with three straight birdies, including a 25-footer at the 18th.
"The first five holes were up there, quite a bit of a roller-coaster," said Holmes, who had the ace, one birdie, one par and one double-bogey through five.
Holmes, seeking a third win in the Arizona desert, has played with elbow trouble for years and said he improved mid-round after attention from his trainer around the ninth and 10th holes.
"Still hurt a little bit, but not as much," Holmes said. "I putted really well on the back. Hit it in good spots and made some good putts."
Among the top names in the field, Spain's Jon Rahm led a group of 10 players on 67 that also included Japan's Hideki Matsuyama.
Defending champion Rickie Fowler left himself work to do to make the weekend after opening with a three-over par 74.
Leading first-round scores on Thursday in the US PGA Tour Phoenix Open at TPC Scottsdale in Arizona (USA unless noted, par-71):
61 - Wyndham Clark
63 - Billy Horschel
64 - JB Holmes
65 - Tom Hoge, Harris English, An Byeong-hun (KOR), Bud Cauley
66 - Nate Lashley, KJ Choi (KOR), Im Sung-jae (KOR), Adam Long, Hudson Swafford
67 - Branden Grace (RSA), Kang Sung (KOR), Xander Schauffele, Jon Rahm (ESP), Hideki Matsuyama (JPN), Scott Piercy, Brandon Hagy, Keegan Bradley, Zach Johnson, Patrick Rodgers