Jeju - Defending champion Brooks Koepka needed a late eagle to card a three-under par first round at the CJ Cup on Thursday, but found himself five shots behind local hero An Byeong-hun, who had the galleries rocking.
World No 1 Koepka endured a rollercoaster round at Nine Bridges on South Korea's Jeju Island with three bogeys, four birdies and the stunning eagle three on the long 18th.
"Just a little sloppy there," said Koepka.
"I felt I hit the ball good but the wind was so light I felt like it was switching a bit.
"I think this golf course is a little bit easier if it blows a little bit, the wind is more consistent."
Koepka said all he needed to improve was to stop making "dumb mistakes," like on the 12th, when he carved his approach shot left into thick rough, resulting in a bogey six.
"Hit it left and long there, just trying to get too cute instead of just putting the ball on the green," he said.
"As long as you put it in the fairway out here you're going to give yourself some chances."
An seemed a little surprised that he had managed eight birdies in a flawless round of 64, including three in a row from the 11th, as he ripped apart the picturesque 7 241-yard Nine Bridges layout.
"It was a strange day," said An, the world No 48.
"During the practice rounds I wasn't striking the ball at all well. I was worried because I didn't hit it well at the range this morning. But as the round went on, I got my feel back."
Hot on the South Korean's heels are Chile's Joachin Niemann, one shot back after a seven-under 65, and Jason Day, who made a perfect seasonal debut after a seven-week layoff with a bogey-free 66.
The 20-year-old Niemann earned his first PGA Tour win at The Greenbrier last month while former world number one Day is chasing a Presidents Cup wildcard.
Australia's Day said such a solid start would do no harm to his chances of making the International team for the match on home soil at Melbourne in December.
"Of course I want to be on the team and go down there and play," he told after his round.
"I've just got to focus day to day. Today was great, check off the box and then move on to tomorrow.
"I want to try and focus on winning this tournament and if I do that then everything will take care of itself."
Another former No 1, Jordan Spieth, has endured a torrid couple of years with no wins since The Open in July 2017, but felt he was on the right track after an opening 70 in his first event for almost two months.
"All in all two-under after seven weeks off is pretty solid start," Spieth said.
"I definitely thought it got better as the round went on.
"Even the double I made I didn't miss a swing. It was just in the lip of a bunker and then I flew a green so they were good shots.
"That's what I'm looking for to build the confidence."
Scores after the first round of the PGA Tour's CJ Cup at Nine Bridges Golf Club, Jeju Island, South Korea (par 72):
64 - An Byeong-hun (KOR)
65 - Joaquin Niemann (CHI)
66 - Jason Day (AUS)
67 - Cameron Smith (AUS), Hwang Jung-gon (KOR), Danny Lee (NZL), Charles Howell III (USA), Charley Hoffman (USA)
68 - Chez Reavie (USA), Justin Thomas (USA), Graeme McDowell (NIR), Lee Soo-min (KOR), Im Sung-jae (KOR), Rafael Cabrera-Bello (ESP)
69 - Emiliano Grillo (ARG), Hideki Matsuyama (JPN), Lee Kyung-hoon (KOR), KJ Choi (KOR), Kim Si-woo (KOR), Viktor Hovland (NOR), Ian Poulter (ENG), Tyrrell Hatton (ENG), Ryan Moore (USA), Max Homa (USA), Kevin Streelman (USA), Brooks Koepka (USA), Collin Morikawa (USA), Kiradech Aphibarnrat (THA)
70 - Luke List (USA), Chase Koepka (USA), Andrew Putnam (USA), Kevin Tway (USA), Ryan Palmer (USA), J.B. Holmes (USA), Jordan Spieth (USA), Phil Mickelson (USA), Dylan Frittelli (RSA), Corey Conners (CAN)
71 - Branden Grace (RSA), Rory Sabbatini (SVK), Lee Hyung-joon (KOR), Adam Schenk (USA), Wyndham Clark (USA), Harold Varner III (USA), Gary Woodland (USA), Billy Horschel (USA), Tommy Fleetwood (ENG)
72 - Scott Piercy (USA), Brian Stuard (USA), Kevin Na (USA), Nate Lashley (USA), Marc Leishman (AUS), Matt Jones (AUS), Kang Sung-hoon (KOR)
73 - Chang Yi-keun (KOR), Sergio Garcia (ESP), Abraham Ancer (MEX), Adam Long (USA), Pat Perez (USA), Matthew Wolff (USA), Jhonattan Vegas (VEN)
74 - C.T. Pan (TPE), Vaughn Taylor (USA), Jazz Janewattananond (THA), Joel Dahmen (USA), Lucas Glover (USA), Keith Mitchell (USA), Troy Merritt (USA), Won-joon Lee (AUS), Park Sang-hyun (KOR), Ham Jung-woo (KOR), Lee Tae-hee (KOR)
75 - Chesson Hadley (USA)
76 - Michael Kim (USA), Moon Kyong-jun (KOR), Kim Meen-whee (KOR), Danny Willett (ENG)
78 - Bae Yong-jun (KOR)