Canadian Adam Svensson earned a one-stroke lead after round one of the Sony Open in Hawaii, where Jordan Spieth stumbled in his first appearance of the season.
Svensson carded a nine-under-par 61 – highlighted by seven birdies and one eagle – to top the leaderboard at Wai'alae Country Club in Honolulu on Thursday.
The 25-year-old, whose best finish last season was a tie for 39th, was trailing clubhouse-leader Andrew Putnam but leapfrogged him after four consecutive birdies on the back nine and one final one on the par-five 18th hole.
American Putnam has sole possession of second place following his first-round 62 at the PGA Tour tournament, while Matt Kuchar (63) is a stroke further back.
A handful of golfers are tied inside the top 10, including Brandt Snedeker, Jason Dufner and Cameron Smith, who are in a seven-way tie for seventh place after shooting 66s.
Justin Thomas – the 2017 champion – did not have much luck late, but when it did come it was certainly exciting following three-under-par 67.
The nine-time tour winner was flawless on the front nine. He opened with a birdie on the par-four first hole and carded another birdie just three holes later.
Before he made the turn, Thomas rolled in a 12-foot putt for an eagle on the 9th hole. But, the back nine was a different story.
Thomas had four bogeys, three of which were sandwiched in between one more birdie and an eagle to close out the round.
He found a bunker on the par-five 18th hole and looked as if he might finish with yet another bogey. However, his bunker shot got the perfect bounce off the green and one more off the flagstick for an impressive ending.
Marc Leishman, Davis Love III and defending champion Patton Kizzire ended the day level alongside Thomas in 17th place.
American star Spieth, meanwhile, struggled after opening the tournament with a three-over-par 73.
It was a difficult day for 11-time PGA Tour champion Spieth, who had four bogeys and just one birdie to be tied for 127th and 12 shots off the pace.