Korea’s Byeong Hun An delighted the home crowd by carding an eight-under-par 64 to lead the CJ Cup Nine Bridges on Jeju Island.
An fired eight birdies in a bogey-free round to lead Chile’s Joaquin Niemann by a shot, with former world number one Jason Day a shot further back following a 66.
Defending champion Brooks Koepka is five shots off the pace after a 69 matched by the English pair of Ian Poulter and Tyrrell Hatton and Norway’s Viktor Hovland, whose 18th consecutive round in the 60s established a new PGA Tour record.
Graeme McDowell sit four shots off the lead after a very tidy opening round of 68 which included four birdies and no bogeys.
Koepka’s erratic round included four birdies, three bogeys and an eagle on the par-five 18th and the world number one said: “Just needed to clean up a few things, missed a couple of short putts, a little sloppy there, but other than that I thought I hit the ball good.
“The wind was just so light today it felt like it was switching quite a bit and it made a difference on a couple of holes.
“Honestly I think this golf course is a little bit easier if it blows. If it blows a little bit the wind is a little bit more consistent.”
Day, who is hoping International Team captain Ernie Els will give him a wild card for December’s Presidents Cup at Royal Melbourne, boosted his chances by carding six birdies in a bogey-free 66.
“It is certainly disappointing not to make the team on my own merits, but it is a reminder that nothing is given to you in this game,” the Australian said.
“I certainly want to be on the team and believe I can be an asset to the Internationals. Being in my home country certainly gives me an edge and I’ve had some success on the sandbelt (courses) and Royal Melbourne in the past.”
Collated first round scores in the USPGA Tour The CJ Cup at Nine Bridges, Nine Bridges, Jeju Island, Korea (USA unless stated, par 72):
64 Byeong-Hun An (Kor)
65 Joaquin Niemann (Chi)
66 Jason Day (Aus)
67 Danny Lee (Nzl), Cameron Smith (Aus), Jung-Gon Hwang (Kor), Charley Hoffman, Charles Howell III
68 Justin Thomas, Graeme McDowell (NIrl), Rafael Cabrera-Bello (Spa), Sungjae Im (Kor), Chez Reavie, Soomin Lee (Kor)
69 Hideki Matsuyama (Jpn), Viktor Hovland (Nor), Kyoung-hoon Lee (Kor), Si Woo Kim (Kor), Kevin Streelman, Brooks Koepka, Emiliano Grillo (Arg), Max Homa, Kiradech Aphibarnrat (Tha), Collin Morikawa, Ian Poulter (Eng), Tyrrell Hatton (Eng), Kyung Ju Choi (Kor), Ryan Moore
70 Luke List, Andrew Putnam, Ryan Palmer, Phil Mickelson, J.B. Holmes, Chase Koepka, Kevin Tway, Dylan Frittelli (Rsa), Corey Conners (Can), Jordan Spieth
71 Hyungjoon Lee (Kor), Adam Schenk, Rory Sabbatini (Svk), Harold Varner III, Gary Woodland, Branden Grace (Rsa), Wyndham Clark, Tommy Fleetwood (Eng), Billy Horschel
72 Kevin Na, Brian Stuard, Matt Jones (Aus), Sung Kang (Kor), Marc Leishman (Aus), Nate Lashley, Scott Piercy
73 Matthew Wolff, Abraham Ancer (Mex), Pat Perez, Yi-Keun Chang (Kor), Sergio Garcia (Spa), Adam Long, Jhonattan Vegas (Ven)
74 Vaughn Taylor, Lucas Glover, Sung Hyun Park (Kor), Won Joon Lee (Aus), Joel Dahmen, Jazz Janewattananond (Tha), Tae Hee Lee (Kor), Cheng-Tsung Pan (Tai), Keith Mitchell, Troy Merritt, Jeongwoo Ham (Kor)
75 Chesson Hadley
76 Whee Kim (Kor), Michael Kim, Danny Willett (Eng), Kyong-jun Moon (Kor)
78 Yongjun Bae (Kor)
