Seamus Power is six shots off the lead after his opening round at the Sentry Tournament of Champions in Kapalua, Maui.
The Waterford native carded a two-under 71 around the Hawaii course, with six birdies - including his opening hole and three in succession on 14, 15 and 16, as well as two bogeys and a double bogey.
Australia's Cameron Smith leads the way after carding a pair of eagles en route to an eight-under-par 65 to claim a one-shot lead.
His solo lead held up when reigning FedEx Cup champion Patrick Cantlay was unable to get up-and-down for birdie on the closing par-5 18th hole. Cantlay settled for par and is tied with world number one Jon Rahm and Daniel Berger at seven under.
Another shot off the pace is Kevin Na, South Korea's Sung-jae Im and South Africa's Erik van Rooyen.
Smith bogeyed the second hole before getting his round going with a birdie on the following hole. He reached the par-5 fifth hole in two shots and sank his first eagle putt of the day from 44 feet.
Smith was three under when he reached the par-4 13th hole. He reeled off a pair of birdies and then drained a 37-foot eagle putt on the par-5 15th. Another birdie on 16 made Smith five under over a four-hole stretch, but he was unable to maintain the torrid pace as he parred out over his final two holes.
"I just needed those two eagles to get a really low one happening," he said.
"Obviously two really long putts and probably quite fortunate that they went in, but they went in."
Meanwhile, Rahm started off well in his effort to hold off Collin Morikawa for the top spot in the Official World Golf Ranking for at least another week.
The Spaniard reeled off three consecutive birdies on the front nine and then four more over his final six holes in posting a bogey-free round. Rahm is guaranteed of remaining number one if he finishes first or second, but Morikawa is only two shots behind at five under.
"Not that I'm surprised that I played good, but it's really good to come out and start the year off the right way," he said.
Two-time event champion Justin Thomas is tied for last in the 38-player field at one over with 2015 winner Patrick Reed. Meanwhile, 2016 champion Jordan Spieth is six shots off the lead at two under along with Phil Mickelson, who is playing in the event for the first time in 21 years.
Defending champion Harris English scuffled to an even-par 73 as he attempts tobecome the first player to successfully defend his title at the event since Geoff Ogilvy in 2009-10.
Smith entered the week 21st in the OWGR and qualified for the event for the first time courtesy of his win with fellow Australian Marc Leishman at the Zurich Classic. He played three times during the fall swing, but has not teed it up since tying for fourth at The RSM Classic in November.
"I think six or seven weeks off, a bit of a refresh," he said. "I didn't play a lot through the fall, so it kind of felt like I've had a really long break."
With the winning score being 20 under or better in 10 of the previous 13 events at the Plantation Course at Kapalua, Smith anticipates he'll need to keep the pedal to the medal over the final three rounds.
"The course is really receptive, it's going to be low-scoring all week unless the wind gets up," he said. "I don't think that's meant to be the case, so,yeah, it will probably take something, maybe three more of those (low rounds) to get the job done."