Englishman Harry Hall fired a career-low, 8-under 62 to establish a three-stroke lead at the Charles Schwab Challenge after one round on Thursday in Fort Worth, Texas.
Hall picked up eight birdies without a bogey at the famed Colonial Country Club to put himself clear of second-place Harris English (65).
A tie for third at 4-under 66 includes Tom Hoge, Adam Schenk, Robby Shelton and Andrew Putnam.
Hall lapped the field in Strokes Gained: Putting, making a 17-foot birdie putt at the par-4 seventh hole and saving par from 28 feet out at the par-4 15th.
"My putting was great," Hall said. "Been waiting for a round like that with the putter because I know I can get hot, and consistently I'm really good. Yeah, that was nice to hole some putts out there today."
He also chipped in from off the green for birdie at the par-4 12th before rolling in his eighth and final birdie at No 18 to get to 8 under.
Hall, 25, has just three top-10 finishes in his young PGA Tour career, with two coming this season at the Puerto Rico Open and Mexico Open.
"This feels nice to be on the leaderboard," Hall said. "Hopefully I can keep the gap there between the rest of the field this afternoon."
The only player to come close was English, once a top-10 player in the world who had to miss time to undergo hip surgery and is starting to make a comeback. He had six birdies and one bogey, including back-to-back birdies at Nos. 8 and 9 to conclude his round.
"It's been trending in the right direction," English said of his game. "Played good in some elevated events, and coming to a place this week that I really, really enjoy. I love the town. I love this golf course, and I've some good finishes here."
Hoge, who played collegiately in Fort Worth at TCU, holed out from the seventh fairway from 154 yards for an eagle that boosted him to 4 under.
"I heard it hit the pin," Hoge said. "It was interesting, when we got up there, usually if you slam one in there, it will beat up the hole pretty good. The hole was clean, no ball marks around the hole. Looks like it just flew in perfect."
Defending champion Sam Burns and world No 1 Scottie Scheffler, whom Burns beat in a playoff to win last year, each shot 3-under 67. They were part of a large tie for seventh that also included Max Homa, Billy Horschel and South Korea's Si Woo Kim.
Playing on a sponsor's exemption, Michael Block posted an 11-over 81 and was in last place out of 120 golfers.
Block, a 46-year-old club professional, is coming off a dream week at the PGA Championship, where he shot three rounds of 70 and a 71 to tie for 15th while winning over plenty of new fans.
Block carded seven bogeys before posting double bogeys at Nos. 15, 16 and 18. One of his two birdies came at the par-3 fourth, where he nearly knocked in a hole-in-one before converting from 4 feet. Block had a hole-in-one on Sunday at the PGA.