A "tired'' Jason Day roared around the famous Sawgrass in a course-record equalling 63 with nine birdies to seize the lead in The Players in Florida today.
Day, the world No. 1, began with a bombed birdie at his first hole, the 10th, and never looked back.
He made birdies at the first three holes that he played, went through the back nine in 32, then poured in five more birdies on the front side, threatening the course record held by Greg Norman, Martin Kaymer, Roberto Castro and Fred Couples.
He missed a birdie opportunity at the eighth that would have given himself a chance of take the record, but closed with a birdie at the ninth to tie it. "I'll take a tied course record,'' he said afterward.
Day had nine birdies, no bogeys, and just 24 putts on a day when his putter was white hot. "I just played solid tee to green and when I got to the green, I felt very confident with my putter,'' he said.
The Australian was in some kind of zone, although he told the tournament broadcaster later that he was fatigued. "To be honest, I just felt tired all day,' he said. "I was so distracted and I felt so tired and I was trying to grind it out as much as possible. It's been a long week and so hot, I just felt tired.''
Day has never won the Players, often called the fifth-major and worth $US10.5 million. He leads by two shots from a cluster of players on 65 — Justin Rose, Cameron Tringale, Shane Lowry, Bill Haas and Brendan Steele.
Aaron Baddeley (69) was the best of the other Australians, while Marc Leishman carded a 70. Adam Scott suffered a calamitous quadruple-bogey eight at the par-four 18th hole, with two balls in the water hazard, that ruined what was otherwise a good day.
Scott was three-under through 17 holes but hooked his two-iron tee shot into the hazard, then after a penalty drop, flared his third shot right, past the grandstand and watched it run miles away down a cart path. His next shot flopped on the green but trickled back into the water, and two putts later he finally holed out and signed for a 73.
John Senden (75), Matt Jones (78) and Steven Bowditch (80) all struggled.