Los Angeles - Tony Finau set the early pace at the Charles Schawb Challenge on Thursday, reaping the rewards from a change of putting grip to card a six-under-par 64 to claim the clubhouse lead at Colonial Country Club in Texas.
The world No 15 took a one-shot lead after posting seven birdies and one bogey as he chases only his second PGA Tour victory.
Finau, who managed a fifth place finish in the Masters last month but struggled in the PGA Championship, finishing tied in 64th, started slowly before making back-to-back birdies on the third and fourth holes.
His opening birdie on the third came after he rolled in a 19-foot putt, and he backed it up on the par-three fourth by sticking his tee shot to within three feet for a simple tap-in.
A bogey on the fifth threatened to check Finau's momentum, but he responded with back-to-back birdies on the 7th and 8th holes to reach the turn at three under.
A hat-trick of birdies on the 11th, 12th and 13th saw Finau vault up the leaderboard.
Once again, the 29-year-old relied on a red-hot putter to pick up shots, draining putts of 24 feet and 26 feet to bag his final two birdies of the day.
Finau, who also saved a par by making a 30-foot putt during his round, later revealed he had changed his putting grip after a disappointing showing in the PGA last week.
"I haven't been putting great I feel like, and standing over the ball the most important thing is, 'Do you feel like you're going to make the putt or not?,'" Finau said.
"Outside of everything else, 'Do you believe you can make the putt?' So for me, I needed to switch something."
Jordan Spieth and Roger Sloan meanwhile were a shot back from Finau after both posting five-under-par 65s.
Spieth, coming off a share of third place at the PGA Championship last week, had a wild round comprised of eight birdies, a double bogey and a bogey.
The 25-year-old Texan managed to finish with a flourish however, with a birdie on his final hole of the day.
Spieth believes his recent form indicates a protracted slump may be over.
"I know what I have needed to work on and I knew it was going to take a lot of time," Spieth said.
"It's nice to see some results off what I believe is the progress I've been making. At the same time, it's one round. I've got to keep my head down and keep working."
Spieth and Sloan are two ahead of eight players tied on three under.
Leading scores after Thursday's first round of the US PGA Tour Charles Schwab Challenge event (par-70, USA unless noted):
64 - Tony Finau (USA)
65 - Roger Sloan (CAN), Jordan Spieth (USA)
67 - Jonas Blixt (SWE), Ronald Henry (USA), Chesson Hadley (USA),
Scott Brown (USA), Jason Dufner (USA), Jimmy Walker (USA), Peter Uihlein
(USA), Trey Mullinax (USA), Nick Watney (USA)
68 - Mackenzie Hughes (CAN), Anirban Lahiri (IND), Abraham Ancer
(MEX), Rory Sabbatini (SVK), Ryan Palmer (USA), Kevin Tway (USA), Josh
Teater (USA), Cheng Tsung Pan (TPE)
69 - Emiliano Grillo (ARG), Nick Taylor (CAN), Benjamin Silverman
(CAN), Corey Conners (CAN), An Byeong-Hun (KOR), Danny Lee (NZL), Tyrone
Van Aswegen (RSA), Kevin Streelman (USA), Andrew Putnam (USA), Bill
Haas (USA), Scott Langley (USA), Sam Burns (USA), Jim Furyk (USA), Brian
Gay (USA), Nate Lashley (USA), Paul Casey (ENG), Matthew Fitzpatrick