Rory McIlroy overcame a stuttering start to roar into the mix with two eagles in three holes in the Genesis Invitational at Riviera.
The Holywood star (30) had to dig deep for his first seven holes as he followed a three-putt bogey at his third hole with some brilliant scrambling before flexing his muscles to card a three-under 68.
After curling home a 12-footer for par at the 16th, his seventh, he rifled a 290-yard three-wood to the heart of the 596-yard 17th and rolled in a 35-foot eagle putt to move into the red.
A bogey at the 18th was only a minor blip as he bounced back immediately with another eagle from just five feet at the first .
"It was good after the start," said McIlroy, who birdied the tricky fifth and ended his day four shots behind Matt Kuchar, who fired a seven-under 64 to lead by three shots.
"One-over through seven, missed a couple of short ones early on and went through a stretch of missing a lot of greens.
"But I got it up and down on 13, 14 and 15, and the eagle on 17 kick-started things a little bit."
Admitting his par save at the 16th was key, he added: "There are no easy putts on this golf course and that was nice.
"I feel that part of my game helps me stay in rounds, and putting like that gives you a little bit of momentum going to the next tee.
"You hit a couple of good shots and get a bonus by holing a long one and all of a sudden you are one-under-par and things are looking okay again."
McIlroy matched Patrick Cantlay and outscored Dustin Johnson by four shots as World No.2 Brooks Koepka eased to a 69.
Kuchar had set the early clubhouse target on seven-under-par thanks to a bogey-free 64, with Henley and Lee three shots behind, with many players still to complete their opening rounds.
Tournament host Tiger Woods, who is seeking a record 83rd PGA Tour title and a first win at Riviera, made the ideal start with an eagle from 25ft on the first. That was the start of a stunning four under par front nine, out in 31, before back nine struggles left him two under at the end of the day.
Meanwhile, Royal Dublin's Niall Kearney carded a two-under 71 on the Links at Fancourt to lead the Irish challenge in the Challenge Tour's Dimension Data Pro-Am.
South Africa's Christiaan Bezuidenhout shot an 11-under 61 on the Outeniqua Course to lead by a shot from Spain's Santiago Tarrio as Robin Dawson shot 73 at the Links and Gavin Moynihan a two-over 74 on the Montagu Course.
On the MENA Tour, Portmarnock's Conor Purcell closed with a 69 and pocketed a career-best cheque for $5,000 (€4,600/£3,800) when he tied for third on 10-under, three shots behind France's Sebastien Gros in the NEWGIZA Open in Cairo.
In amateur golf, four Irishmen finished in the top 10 as South Africa's Casey Jarvis (16) fired a seven-under 65 to romp to an incredible nine-shot win on 25-under in the South African Stroke Play at Randpark.
Dundalk's Caolan Rafferty shot 67 to finish third on 15-under with Mallow's James Sugrue (68) three shots further back in sixth as Northern Ireland's Tom McKibbin (67) and Hermitage's Rowan Lester (75) tied for seventh.
In the Portuguese Amateur, Castle's Robert Moran is just four shots off the lead on six-under at halfway after a second-round 70.
Meanwhile, Jordanstown ace Stephanie Meadow is four shots off the lead after the opening round at the ISPS Handa Women's Australian Open.
Meadow's three-under-par has her trailing England's Jodi Ewart Shadoff, who shot a blemish-free seven-under-par at Royal Adelaide.