Sam Saunders upstaged a high-profile field to set the pace after a fog-delayed opening round at the Genesis Open in California.
Saunders, the grandson of the late Arnold Palmer, fired a blemish-free 64 at Riviera Country Club to move two shots clear of the chasing pack.
Dustin Johnson, one of three players who could end the week as world No 1, is part of a five-way tie on five under, with Phil Mickelson and Padraig Harrington part of the group a further stroke back.
Just over an hour’s action was lost early in the morning due to fog, leaving a number of players unable to complete their opening round before bad light saw play suspended.
Beginning on the back nine, Saunders posted a two-putt birdie at the 11th and drained a 25-footer at the next on his way to reaching the turn in 32.
A close-range gain at the first briefly moved Saunders in a five-way tie for the lead, which included Johnson and Mickelson, before claiming outright advantage with a birdie at the fifth.
The 29-year-old, who is only in the field through a sponsor’s invite, then picked up another shot at the seventh and closed his bogey-free round with a two-putt par at the last.
Johnson had temporarily held a two-shot lead thanks to four birdies in a five-hole stretch around the turn, only for him to lip out from eight feet for bogey at the fourth.
A run of pars along the closing stretch left Johnson on five under alongside J.T Poston and Daniel Summerhays, who didn’t drop a shot in his first round.
The trip were joined late in the day by Australia’s Cameron Percy and Brett Stegmaier, after the American birdied five of his opening seven holes.
One-time joint-leader Pat Perez sits in the large group on four under alongside Billy Hurley III, who bogeyed his final hole, with Byeong Hun An also in the group after opening with a hat-trick of gains.
Former world No1’s Adam Scott and Luke Donald posted matching 68s, with English pair Justin Rose and Paul Casey a further shot back.
Play will resume at 7am local time (3pm GMT) on Friday, with World No 1 Jason Day and Phoenix Open champion Hideki Matsuyama among those yet to finish their round.
Watch the Genesis Open throughout the week live on Sky Sports 4 – your home of golf. Live coverage begins on Friday from 7pm.