Rory McIlroy shrugged off a rain delay of almost two hours which raised the prospect of a Monday finish in the US PGA Championship at Valhalla.
With the course already saturated, a torrential downpour saw play suspended at 12:53pm local time, more than two hours before the final pair had been scheduled to tee off.
Play was eventually able to resume at 2:44pm with McIlroy and Austria's Bernd Wiesberger now due to start at 4:19pm, meaning they faced a race against time to finish before darkness descended in Louisville.
McIlroy will start the round one shot clear of Wiesberger.
If necessary, there would be a three-hole aggregate score play-off on the 13th, 17th and 18th holes.
"I will hang around until next week to try to win this thing. It doesn't bother me in the slightest," McIlroy insisted before being forced to change the passcode on his phone after it was clearly shown on TV as he waited in the clubhouse.
"Passcode changed... Now time to play some golf!" the world number one wrote on Twitter.
With rain having been forecast, it raised questions as to why tee times had not been brought forward or play started from two tees.
The Open Championship employed a two-tee start for the first time in its history last month due to the significant risk of thunderstorms at Royal Liverpool during Saturday's third round.
Play got under way at 9am from both the first and 10th tee, with the field split into groups of three rather than two.
It looked to have been an unnecessary precaution when there was no disruption to play and heavy rain which made life difficult for the early starters had stopped as the leaders went out at 11am.
But the rain returned as McIlroy gave his post-round press conference, making it difficult to hear what the 25-year-old said and leaving standing water on some of the greens.
Asked if that vindicated the decision, McIlroy laughed and pointed to the media centre roof before adding: "Definitely. I think it's the second best decision the R&A made this year, the first being bringing the Open back to Portrush."
McIlroy was looking to claim his second major in four weeks, and the fourth of his career, which would make him the first player since Padraig Harrington in 2008 to win back-to-back majors.
Lifting the Wanamaker Trophy for the second time would also see the Northern Irishman become the third youngest player after Tiger Woods and Jack Nicklaus to win four majors, just one less than the total won by the late Seve Ballesteros and two behind Nick Faldo.
It is the fourth time McIlroy has held the 54-hole lead in a major, the first leading to heartache in the 2011 Masters when he was four ahead entering the final round at Augusta only to collapse to a closing 80.
Two months later he bounced back in spectacular style to win the US Open by eight shots at Congressional before winning the 2012 US PGA by the same margin at Kiawah Island.
Last month he led from start to finish at Royal Liverpool, taking a six-shot lead into the final round before going on to win by two from Sergio Garcia and Rickie Fowler.
McIlroy began with a par on the first to remain one ahead of Wiesberger but the challengers were mounting behind as the players took advantage of the receptive greens.
Ernie Els had raced to the turn in 30 with four birdies in a row from the third and another on the ninth, the South African moving to 10 under par as a result and giving him a chance to record the first ever sub-63 score in a major championship.
Playing partners Henrik Stenson and Mikko Ilonen had both birdied the first and third to move to 11 under alongside Phil Mickelson, who had holed from 30 feet on the first.
Els remained on track with his sixth birdie of the day on the 11th but McIlroy made his first mistake on the third, three-putting from long range on the par-three.
That dropped him back into a tie for the lead with Wiesberger and Mickelson, who had birdied the third from 10 feet, and birdies from Fowler and Stenson soon made it a five-way tie on 12 under.