A weather delay at the Genesis Open prompted the PGA Tour to make the rare move of wiping out players' scores, and the first round of action in Pacific Palisades, Calif., wound up being suspended due to darkness Thursday.

The first 23 golfers completed one hole or two holes at Riviera Country Club before a rain delay began. During the seven-hour delay, the PGA Tour ruled that all first-round scores would be reset.

The tour hadn't made such a decision since the third round of the 2013 Dell Technologies Championship.

In the end, half of the 144-player field never got on the course Thursday, with their first round postponed until today. Among the players who did see action, Jordan Spieth and South Korea's Sung Kang sit atop the leaderboard at 5 under par. Spieth played 12 holes while Kang played 14 holes.

Patrick Rodgers (13 holes) and Jimmy Walker (10 holes) are tied for third at 4 under par. Tony Finau (12) and J.T. Poston (nine) share fifth place at 3 under par, and 10 players are tied for seventh at 2 under par.

Phil Mickelson, who won the AT&T Pebble Beach Pro-Am last week, is tied for 42nd at 1 over par through 12 holes.