World number one Jason Day kicked off The Players Championship in style, tying the course record at TPC Sawgrass via a nine-under 63 on Thursday.
The testing in Ponte Vedra Beach course bought the best out of Day as he went bogey-free, with birdies on his first three holes on the back nine setting him up for a stellar round and a two-stroke lead as Jordan Spieth endured an unspectacular return.
Day went on to birdie the 17th before adding another five to his tally following the turn at the prestigious PGA Tour event.
The nine-time Tour winner, who ended his day with a birdie, is two shots clear of a group of five players, while Spieth is even par.
Back in action for the first time since his stunning collapse at last month's Masters, Spieth had three bogeys and a double-bogey for a 72, a score matched by defending champion Rickie Fowler and Rory McIlroy.
Americans Cameron Tringale, Bill Haas and Brendan Steele are joined by Irishman Shane Lowry and England's Justin Rose at seven under through 18 holes.
Lowry had a quiet front nine, with a birdie on the second and a bogey on the sixth, before he blitzed the back nine with five birdies and an eagle to see out the round.
Tringale almost went error free, but for a fifth-hole bogey, while Rose posted an eagle on the 16th as well as six birdies to amend for his fourth-hole bogey.
Haas and Steele both went bogey-free for their 65s.
A stroke further back is Ernie Els, alongside Brooks Koepka, Francesco Molinari, Hudson Swafford, Daniel Berger and Boo Weekley.
James Hahn - winner of the Wells Fargo Championship - carded a first-round 67 to be four shots behind Day.
Phil Mickelson and Adam Scott are at two-under alongside Masters champion Danny Willett.