Wyndham Clark recorded a bogey-free, 10-under-par 61 on Thursday, and he holds a two-shot lead after the opening round of the Waste Management Phoenix Open in Scottsdale, Ariz.
Billy Horschel sits in second place after an 8-under 63 at TPC Scottsdale. J.B. Holmes is third at 7 under following a round that included a hole-in-one.
Tom Hoge, Harris English, Bud Cauley and South Korea's Byeong Hun An are tied for fourth at 6 under, and five players share eighth place at 5 under.
Clark, who turned pro in 2017, is still looking for his first PGA Tour. He recorded four career top-10 finishes in 43 previous events.
Starting Thursday in the back nine, Clark produced a run of five birdies in six holes. On the front nine, he added birdies at Nos. 1-3 and No. 7-8.
Horschel's bogey-free round was highlighted when he sank a 5-foot eagle putt at the par-5 third hole. He nearly added another eagle on the par-4 sixth hole, when his 110-yard approach shot landed inches from the cup.
Holmes aced the 175-yard fourth hole, and part of a wild stretch in which he went double bogey-birdie-ace-bogey on Nos. 2-5. He also closed with three consecutive birdies even though he was battling "tennis elbow."
"My arm was hurting pretty good on the front (nine), so I was just trying to get it out there, get through it," Holmes, who had a therapist work on his elbow on the 10th hole, told the Golf Channel. "I'll go do some work on it now.
"Just one of those days where everything kind of went my way."
English and An thrived while competing in the same group.
"It's always nice when the guys you're playing with are playing well," English told the Golf Channel. "It's nice to feed off each other like that, to see some good shots going next to the flags and a lot of fairways hit. It's nice to get in that groove."
Defending champion Rickie Fowler had five bogeys in a seven-hole span, and he finished at 3 over, tied with Jordan Spieth, among others, for 110th place.
NOTES: Justin Thomas, who is tied for 23rd at 3 under, has joined Tiger Woods, Jimmy Walker and Dustin Johnson as the only players to hold the No. 1 spot in the FedEx Cup standings for 30 weeks in their careers. ... Fowler's previous best finish in five title defenses was a tie for 46th at the 2016 Dell Technologies Championship. ... Spieth is ranked No. 51, the first week he has been outside of the top 50 since 2013. He needs to move within the top 50 by Feb. 17 to qualify for next month's WGC-Mexico Championship. ... Bubba Watson (2 under, tied for 31st) has four career top-five finishes at TPC Scottsdale. ... Only nine hole-in-ones have been recorded in event history at the famous par-3 16th hole.