Bryson DeChambeau captured his second PGA title with a birdie at the second play-off hole to win the Memorial.
The 24-year-old world number 38, one ahead overnight, had finished 15 under with Kyle Stanley and Byeong Hun An.
Englishman Justin Rose needed a win to become world number one but a two-under 70 left him three back in joint sixth.
Northern Ireland’s Rory McIlroy had five birdies in a 69 to finish joint eighth at 11 under, but Tiger Woods shot a 72 and was six shots adrift.
Players had been sent out in groups of threes earlier than usual on the final day, from both the first and 10th tees, because of expected storms at Muirfield Village in Ohio.
Although the wind increased in the early afternoon sunshine, the bad weather failed to materialise but the pressure of the closing stages saw some dramatic developments.
American Stanley, whose chances appeared to have ended with a double bogey at the 12th, came back to tie for the lead with four consecutive birdies, culminating in a huge sloping 30-footer from the edge of the 17th green.
But at the final hole his drive hit a tree on the right side of the fairway and careered into an unpleasant lie in the thick rough on the left and he dropped a shot to close with a 70.
That left DeChambeau with an eight-foot putt for par and the title but it drifted left and he signed for a one-under 71.
South Korean An, who had birdied two of the last four holes for a 69 to complete four sub-70 rounds, joined the Americans in the sudden death play-off.
On the first extra hole – the 18th – Stanley had a horrendous stance in the rough and made a bogey to bow out as DeChambeau and An both made par and then returned to the tee to take on the 484-yard par four again.
An missed the green with his approach but played a deft chip to three feet.
However, DeChambeau rolled in a nine-footer on a similar line to the one he missed in regulation play, to take the title.
Patrick Cantlay, one of three players sharing second overnight, had four birdies in the first eight holes and was two shots ahead at the turn, but dropped three on the way home and finished 14 under.
Rose, four adrift going into the final round, had two birdies in his first three holes before dropping two shots on the back nine.
Chile teenager Joaquin Niemann, the world number 406 making only his fifth professional start, who was at the top of the leaderboard after both of the first two rounds, mixed five birdies with two double bogeys in a 73 to share sixth with the world number three.
World number one Justin Thomas eagled the 15th and then holed from a bunker to add a birdie at the next, before a birdie at the last gave him a round of 68 and a share of 11th.
Second ranked Dustin Johnson was also in the five-way tie for 11th after seven birdies in his 67.
Phil Mickelson finished with a birdie, his sixth of the day in a round of 68, his eighth top-20 finish of the year.
Woods, seeking his first win since 2013, had two birdies in his first five but endured further frustration with his putter, then drove out of bounds at the 13th and went on to finish in a tie for 23rd with Scotland’s Martin Laird on nine under.
Article source: http://www.bbc.co.uk/sport/golf/44350118