Shane Lowry is eight shots off the lead after the opening round at the RBC Heritage in South Carolina.
The Co Offaly native carded a first-round 70 that leaves him on one-under ahead of Friday's second round.
Australia's Cameron Smith holds a one-shot lead ahead of USA's Stewart Cink after a career-low 62 around the Harbour Town Golf Links course.
Graeme McDowell opened with a 73 that puts him three shots behind fellow major winner Lowry on two over.
Lowry opened with birdies on 10 and 11 before a bogey on 12 in an eventful start to proceedings.
He carded further birdies on 16 and 18 either side of a bogey on the 17th.
Three bogeys and two birdies across his final nine holes eventually saw him home with a 70 on the Par 71 course.
A career-low 62 for Cameron Smith was almost a 61. ?? pic.twitter.com/Cv3y2w2FLY— PGA TOUR (@PGATOUR) April 15, 2021
McDowell, meanwhile, had three birdies and two bogeys on his front nine. But bogeys on the 10th and 15th either side of a double bogey on 12 saw the Northern Irishman slip back from level par and then to three over before a birdie on the 18th lifted him to two over.
But it was Australia's Smith who grabbed the headlines at Hilton Head.
The 27-year-old, who tied for 10th at last week's Masters Tournament and is currently No 26 in the Official World Golf Rankings, recorded his lowest competitive round on the PGA Tour. His bogey-free round featured five birdies on the front and four on the back, including a birdie-birdie finish. He also notched impressive up-and-down saves for par on 13 and 16, and holed out his greenside bunker shot on the par-3 17th.
"Everything just came together," said Smith, a six-year PGA veteran with two titles to his credit (2017 Zurich Classic of New Orleans, 2020 Sony Open). "It was a great day on the green. I was hitting my irons really good, I had lots of good looks and I just took advantage of them.
"I feel like, after last week, chipping around here is a breeze. I was so scared last week, almost on every chip shot, and I feel like I can be really aggressive around here.
"I feel like I can hit the shot I need to hit and I'm going ahead and trying to execute it. I just feel like every shot I'm hitting, I'm just trying to put 100% into it, and on a day like today, it's really rewarding."
Cink opened his round with a tee shot into a water hazard but rebounded with seven birdies and an eagle to grab the early advantage. He had four birdies and the eagle on his back nine.
The 47-year-old posted his best-ever round at Harbour Town following 74 previous professional rounds on the track. Cink comes in confident after finishing tied for 12th at last week's Masters and a top-20 finish in his previous event, The Honda Classic.
After his round, Cink tweeted: "So many good memories at the RBC Heritage. Happy to add today's 63 to that list!"
Tied for third at six-under are Englishman Matt Wallace and WGC-Workday Championship winner Collin Morikawa, while Americans Charles Howell III, Billy Horschel and Harold Varner III shot 66 and are tied for fifth.
Defending champion Webb Simpson shot even-par 72 and stands tied for 66th.
Wallace, who carded a bogey-free round, finished third at the Texas Open at 14-under and was tied for 34th last week at The Masters.