Australia's Jason Day won the PGA Championship in historic style on Sunday, capturing his first grand slam title with a 20-under par total unprecedented in major championship history.(Lahiri Finishes Fifth)
Day carded a five-under par 67 in the final round at Whistling Straits for a 20-under total of 268 -- breaking Tiger Woods's major-record low winning total of 19-under set at the British Open in 2000.
Day, who has endured a bevy of near-misses on golf's biggest stages, was never going to let this one slip away.
From his birdie from a bunker at the second hole, Day was off and running, leaving Masters and US Open champion Jordan Spieth and the rest of the field in the shade.
Spieth carded a four-under par 68 for 17-under 271, holding off England's Justin Rose and South African Branden Grace to finish second and seize the world number one ranking from Rory McIlroy.
His ascent to the top of the world rankings will be some consolation for his inability to join Ben Hogan and Tiger Woods as the only men to win three majors in one year.
"Sometimes there's not much you can do," said Spieth, whose 2015 record in majors remains impressive at two wins, one second place and a tie for fourth.
With Spieth in solo second place McIlroy -- playing for the first time since rupturing an ankle tendon in July -- would have needed a top-six finish to hang on to the number one spot.
His closing 69 put him in 17th place on 279.
"To be number one in the world... is fantastic," Spieth said. "Certainly it was a lifelong goal of mine, and that was accomplished today."
As for beating Day, Spieth said, that just never seemed to be in the cards.
"The key holes were eight through 12 for me today where I really needed to make a statement and couldn't get it to go," said Spieth, who called the outcome the "best loss I think I've ever had."
"I still provided some opportunities to maybe put pressure on at the end and he just shut the door," Spieth said. "He was sitting there swinging as hard as he could off the tee, and every single drive was right down the middle of the fairway."
Day, who will rise from fifth to third in the world rankings, took a two-stroke lead into the final round -- his biggest 54-hole lead at a major after holding at least a share of the top spot through three rounds in both the US and British Opens this year.
His 50-foot birdie putt at the seventh capped a burst of three straight birdies.
Day finished with seven birdies on the day and two bogeys, twice reaching 20-under as his pursuers scrambled in his wake.
He reached 20-under for good with a two-putt birdie from the fringe at the par-five 16th.
At 18, Day rolled his first putt from 45 feet to within a foot, and was already weeping as he tapped in for par and the win.
Grace applied the most pressure, moving within one stroke of Day's lead after a third straight birdie at the seventh.
But Day pulled away with his own birdie burst at five, six and seven, and his lead was never again less than two strokes.
Grace finished third after a 69 for 273, while Rose bogeyed 18 to fall to fourth with a 70 for 274.