Matt Kuchar fired a sparkling seven-under 64 to seize a three-shot lead after the first round of the Genesis Invitational at Riviera Country Club.
South Korea's Lee Kyoung-hoon and Americans Russell Henley, Wyndham Clark, Adam Schenk and Harold Varner shared second on 67 with Rory McIlroy -- newly returned to world number one -- headlining a group of 10 on 68 that also included Australia's Jason Day and former Masters champion Patrick Reed.
Tournament host Tiger Woods on Thursday closed with a bogey to fall out of that bunch, cooling off after a hot start to post a two-under par 69 as he pursues a record 83rd US PGA Tour title.
Woods was still a teenager when he played his first US tour event at Riviera, but he has never won on the classic course in the Pacific Palisades west of Los Angeles in 12 prior tries, and his struggles continued on Thursday.
"I got off to a nice start on the front nine and just didn't hit many good shots on the back nine," said Woods, who opened with an eagle at the first and added two birdies before the turn but had two bogeys without a birdie coming in.
"Made a couple loose swings and made a couple good saves on the back nine for par, but just wasn't able to get any birdies on the back nine," Woods said.
Kuchar, meanwhile, started hot and stayed that way.
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"To shoot a number like this, you kind of do most things well," he added. "I felt like it was just steady golf, a lot of opportunities and I was able to convert on a good number of the opportunities today."