Mexico's Carlos Ortiz is the outright leader after the first round at LIV Golf Portland, finishing five under after his first trip around Pumpkin Ridge Golf Club.
He was on track for a bigger lead than the one stroke buffer he holds, with three birdies from his first four holes after beginning his shotgun start on the ninth tee, before back-to-back bogeys brought him back to the field.
Ortiz finished his round with three birdies on his final five holes, re-taking the lead in the final stages of play.
Dustin Johnson is just one stroke back in outright second place at four under, bogeying his first hole of the day as he started on the 18th, but it would be his only blemish, collecting five birdies and 12 pars the rest of the way.
Rounding out the top-five is Pat Perez, Hideto Tanihara, Wade Ormsby and Branden Grace in a tie for third at three under.
Playing in his first LIV Golf event, Brooks Koepka put in a good showing as one of 13 players to finish under par, tied for seventh along with Hennie du Plessis after their two-under 70s.
Louis Oosthuizen, Martin Kaymer, Scott Vincent and Yuki Inamori are tied for ninth at one under, while big names Patrick Reed and Bryson DeChambeau headline the group at even par.
Koepka's brother Chase Koepka is at one over along with Mexico's Abraham Ancer, winner of LIV Golf's debut event Charl Schwartzel is at two over with Ian Poulter, and Phil Mickelson finished at three over with Sergio Garcia and Kevin Na.