Florida - Top-ranked Jason Day of Australia matched the TPC Sawgrass course record on Thursday, firing a bogey-free nine-under-par 63 to grab a two-stroke lead in round one of the PGA Tour Players Championship.
The 28-year-old Aussie, who captured his first major crown at last year's PGA Championship, has won six times in his past 16 starts and took full advantage of soft greens and top scoring conditions.
"I can't really recall the way that I hit the ball as well as I did today, and then also putting as well as I did," Day said.
The course record of 63 was first achieved by American Fred Couples in 1992, matched by Aussie Greg Norman two years later and equaled by American Roberto Castro in 2013 and Germany's Martin Kaymer in 2014.
Starting on the back nine, Day opened with three birdies in a row and added another at the par-3 17th with its island green. He birdied the first, par-5 second and fourth then closed with birdies at the seventh and ninth holes.
"The temperature was hot, so the ball was going a long way, and when the ball goes a long way, you're coming in with shorter clubs if you hit the fairways," Day said. "We thought the greens were sticking and a lot of guys could attack the pins that we had out there."
Ireland's Shane Lowry, England's Justin Rose and Americans Bill Haas, Cameron Tringale and Brendan Steele shared second on 65 while a pack on 66 included South African four-time major champion Ernie Els, Italy's Francesco Molinari and Americans Hudson Swafford, Daniel Berger and Brooks Koepka.
New Zealand's Danny Lee and Canada's Nick Taylor were in a group on 67 with afternoon starters still on the course.
Els, who stumbled with a six-putt disaster in his opening hole at the Masters last month, eagled the second hole.
"Gave myself some chances, especially early on the front nine, and I made some putts," Els said. "It feels really good."
World number two Jordan Spieth, who defends his US Open title next month at Oakmont, is in his first event since squandering the back-nine lead to lose the Masters last month. He shot 72 after ending his first competitive round since his Augusta National meltdown with a double bogey at the ninth.
England's Danny Willett, who won the green jacket after Spieth's collapse, opened with a 70 in his first start since claiming his first major title.
Leading scores on Thursday after the first round of the US PGA Players Championship (par 72, USA unless noted):
63 - Jason Day (AUS)
65 - Cameron Tringale, Shane Lowry (IRL), Justin Rose (ENG), Bill Haas, Brendan Steele
66 - Francesco Molinari (ITA), Hudson Swafford, Ernie Els (RSA), Brooks Koepka, Daniel Berger, Boo Weekley
67 - Jerry Kelly, Gary Woodland, James Hahn, Danny Lee (NZL), Nick Taylor (CAN), Jhonattan Vegas (VEN), Jonas Blixt (SWE), Ryan Palmer, Zach Johnson, Alex Cejka (GER)
68 - Will Wilcox, Chad Campbell, Paul Casey (ENG), Martin Kaymer (GER), Russell Knox (SCO), Billy Horschel, Kim Si-Woo (KOR), Carl Pettersson (SWE), Hideki Matsuyama (JPN), Steve Wheatcroft