KOHLER - Jason Day seized a two-stroke lead after three rounds of the PGA Championship, where he'll try to hold off Masters and US Open winner Jordan Spieth for a first major title.

Australia's Day survived a late double-bogey to card a six-under par 66 at Whistling Straits on Saturday, his 15-under par total of 201 putting him two strokes in front of Spieth. The 22-year-old Texan birdied six of his last eight holes in a seven-under 65 for 203. But Spieth said he won't be thinking about joining Ben Hogan and Tiger Woods as the only men to win three majors in the same year when he tees off with Day on Sunday.

"Just to try to get my name on the Wanamaker Trophy ... that's the only history I'll be thinking of," said Spieth, who can also seize the number one world ranking from Rory McIlroy, who carded a four-under 68 for a six-under total of 210. "It should be an exciting round tomorrow," said Day, who is looking for a major breakthrough after finishing with at least a share of second in three grand slam tournaments -- with nine top 10 finishes in six years on the game's biggest stages.

An unusually yielding Straits course made for a chaotic leaderboard as player after player surged upward. When the dust settled, South African Branden Grace had the lowest round of the day, a bogey-free eight-under par 64 for a share of third on 204 alongside England's Justin Rose, who dropped into the tie with a bogey at 18 to cap a 68. Germany's Martin Kaymer, trying to reprise his 2010 PGA Championship victory at Whistling Straits, the par-72, 7,501 yard course hugging the shore of Lake Michigan, fired seven birdies in a seven-under 65 for 205.

Matt Jones, the unheralded Aussie who took a two-stroke lead into the third round, kept pace early. He salvaged a bogey after hitting into a hospitality suite at the ninth but dropped four shots in three holes going bogey-bogey-double bogey at 15, 16 and 17 en route to a one-over 73 for 206. He was joined on 10-under by American Tony Finau (69), while American Dustin Johnson and India's Anirban Lahiri tied for eighth on nine-under 207. "There was a lot of low scores out there today," Day said, although he got off to an uneven start alternating birdies and bogeys at his first five holes before his first par of the day at the sixth.

After birdies at nine and 10 let him keep pace with Jones, Day took the outright lead with an eagle at the par-five 11th, where he rolled in a 13-foot putt. He followed with birdies at 13 and 14 -- stringing together six straight holes with scores of three. Then came Day's double-bogey at 15, where he needed two shots to get out of a bunker. "I hit a great drive," Day said, "Hit kind of an average five-iron in there and didn't expect to have so much sand."

He was frustrated not to pull the shot back at the par-five 16th, but drained a 24-footer for birdie at 17. "I'm very pleased with how I'm putting," Day said. "There were some mistakes here and there, but overall I hit a lot of good quality iron shots, hit a lot of great drives out there, drove the ball really well."

Spieth was slow to join the day's birdie blitz, following his opening birdie with nine straight pars before lighting up the back nine with two bursts of three birdies -- from 11 through 13 and from 16 through 18. After missing a putt at 10, Spieth said, he told himself "it's now or never." "I thought that if I could get to 10 (under), if I could get three more, then I would still have a chance. "But 13 (under) is a lot sweeter, so I'll take it."