Rory McIlroy battled back from a three-shot deficit with nine holes to play to win the US PGA at Valhalla in near darkness by one shot from Phil Mickelson, securing back-to-back Major titles in the process and a third consecutive victory.
The 25-year-old from Northern Ireland fired a final-round 68 that sparked into life with an incredible eagle three at the 10th as the American duo of Mickelson and Rickie Fowler looked set to spoil the world number one's day.
However, with the light fading fast in Louisville following a two-hour rain delay that threatened to force a Monday finish, McIlroy dug deeper than he has ever had to in a Major to force his way through the congested leader board and become the fourth youngest golfer in history to have won four Majors.
Sweden's Henrik Stenson had earlier made his move with a sublime front-nine 30 that saw him tie the lead with just nine holes of his championship to go. However, the 38-year-old remains Major-less for now after a level-par inward nine was never going to enough in the soft conditions.
Despite the withdrawals of Matt Kuchar and Jason Dufner through injury, the final leaderboard made for good reading for US Ryder Cup captain even if it was McIlroy who eventually proved victorious over the Fowler and Mickelson pairing.
Jim Furyk, Hunter Mahan, Steve Stricker - Watson's vice-captain - and Jimmy Walker all recorded top-10 finishes in Kentucky, while Brandt Snedeker showed a timely return to form with a four-under 67 on Sunday to lie in tied-13th.
Paul McGinley would have been watching on with a wry smile, however, as McIlroy proved beyond any doubt that right now he is the undisputed best player on the planet, and for good reason.
The 'Rory era'
Following victories at Hoylake and Akron in the Open Championship and the WGC-Bridgeston Invitational, the golfing world had begun to usher in the 'Rory era' - something he was quick to dispel - but the evidence over the last month suggests it can no longer be denied.
After all, on Sunday he overturned a three-shot deficit with just nine holes to play of a Major championship, with the American duo in front of him delivering visible and audible blows throughout the entire round as the raucous Kentucky natives provided a suitable back drop to the drama that was unfolding.
With the morning's early starters out completing formalities, the heavens once again opened over Valhalla, causing entire greens to be deluged; players headed back to the clubhouse while the local wildlife made the most of the temporary ponds forming.
In order to make up for lost time, the PGA of America decreased the amount of time between each tee time which, later, would merely add to the pulsating climax.
McIlroy started off solidly enough, parring his opening two holes with little trouble, but a horrible duffed chip at the par-three third resulted in a bogey four and for the first time on Sunday, the world number one was no longer in the lead.
Pressure on McIlroy
His bogey was not the only reason why, though. Stenson had started off in blistering style, birdieing four of his opening eight holes to jump to -13 alongside Mickelson - who was three under through seven - and Fowler, who after bogeying the third rattled off three consecutive birdies to also lie 13 under.
The pressure was firmly on McIlroy, but he failed to respond immediately. At six, he fired his approach over the green to leave himself another testing up-and-down, and after he again failed to fully commit to his wedge shot, he could not convert from 10 feet and he was suddenly three shots adrift of not just one, but three players.
It needed a champion's response, and it got one. At the par-five seventh, a birdie haven for McIlroy all week, he found the green side bunker with his second and got down in two to record his first gain of the day.
At that point though, he was still two back of the leading trio with none of them able to break away from each other.
The 10th changed all that as Fowler rolled in a beautifully weighted right to left putt to take the outright lead and leave McIlroy three adrift once again, and when Mickelson rolled in a short birdie putt of his own at the par-three 11th, the Northern Irishman's task was beginning to escape him.
Going down in history
What happened next will forever go down in the memory of not just those who witnessed it, but the US PGA at a tournament. Having bombed his drive up to reachable distance, McIlroy pulled out his three wood and hit, without question, the best shot yet of his blossoming career.
His Nike golf ball was dispatched up the left hand side and it looked to be staying there originally, but as it pitched and landed it defied the soft conditions and raced up the green to the flag, leaving a mere six-feet between McIlroy and a Major-saving eagle.
With his putting impeccable, it was never missing - suddenly, with eight holes to go, the Northern Irishman was a single stroke adrift. From then on, his iron play was nothing short of perfect.
Birdie opportunities followed at 11 and 12 thanks to two sublime approaches, but he failed to convert both and with holes running out, he remained one behind both Mickelson and Fowler.
This particular 25-year-old golfer is not what you would consider your average player, though, and when another near-perfect iron shot resulted in a makable birdie effort, he was not going to make the same mistake again. He rolled her in dead centre, and celebrated by offering his biggest display of emotion on a golf course with a vigorous fist-pump.
Once again - but for the first time in what must have seemed like an eternity - McIlroy shared the US PGA lead.
Did the group in front know it? They sure did. Fowler made his second bogey of the day at 14 to fall out of the trio of leaders - where he, unfortunately, would not return - before Mickelson did the same at the par-four 16th to drop back to -14.
It was suddenly all change, and as the light drew in across the spectacularly prepared Valhalla golf course, McIlroy showed no relent in his pursuit of his second straight Major win.
At 17, McIlroy sent yet another driver crashing down the fairway and when his approach left him little more than seven foot for birdie and a two-shot lead heading to the last, the Rory era was on the horizon. He sunk it with considerable aplomb.
Up to this point, it had been one of the most memorable final rounds of a Major championship in recent memory, but was marred by a slightly farcical finish that saw McIlroy play up behind Mickelson and Fowler at the 18th as they frantically tried to finish proceedings.
A hairy moment followed for the leader; his drive narrowly avoided the creek running parallel to the 18th fairway, but once it was confirmed safe, the championship was all-but over.
In typical Mickelson style, he doggedly tried to hole his green-side wedge shot for eagle but when it settled inches from the hole for a tap-in birdie, and Fowler's eagle putt drifted harmlessly past, a par for McIlroy would signal victory.
He splashed out to 15 feet from the greenside bunker and when his first putt, perfectly paced, ran up just short of the hole, he steadied himself, embraced the moment and tapped in to record a third-straight victory worldwide - a run that includes two Majors and a World Golf Championship.
Golf is now entering the Rory era - whether he wants to accept that or not. This is different to 2012, he knows how to handle success now.
McIlroy will head to Augusta now not only chasing the Career Grand Slam, but a third straight Major win. It's 291 days away. Let the countdown begin.
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