Wyndham Clark shot the best score of his short PGA Tour career - a 10-under-par 61 - to take the first-round lead at the Waste Management Phoenix Open in Arizona on Thursday.
The second-year player, who lowered his previous best round by three shots, had a two-stroke lead over fellow American Billy Horschel in Scottsdale.
JB Holmes, boosted by a hole-in-one from 175 yards at the fourth, was next best on seven under.
Former world number one Jordan Spieth and defending champion Rickie Fowler struggled and are three over.
Clark's stellar round came on the heels of three straight missed cuts during which he chipped and putted poorly.
"I actually played really good the last couple of weeks. I just wasn't capitalising," the 26-year-old told the Golf Channel.
"I had a great front nine, felt really good off the tee, gave myself a lot of looks and the putter was hot.
"Then it got kind of fun. It was one of those rounds where everything went right."
Horschel was also pleased to find some form and was quick to credit instructor Todd Anderson with turning things around this week by identifying a couple of small technical flaws in his full swing and putting.
"To come out and put up duds the first two weeks was a really big gut shock, especially after I shot that 80 last week," said the five-times PGA Tour winner Horschel, who rolled in two putts from outside 40 feet, including a 45-footer for an unlikely par at the last.
"Throughout my history, once I get on a little run, especially with the putter, I feel like I can make anything from anywhere on the green," he said.
While Clark and Horschel enjoyed themselves at the most raucous stop on the PGA Tour, gallery favourites Fowler and Spieth did not join the party.
Fowler had seven bogeys, while Spieth started poorly with two dropped shots and could not right the ship.
Three-times major champion Spieth has fallen outside the top 50 in the rankings for the first time since 2013 and is currently ranked 51st.