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A dramatic late stumble from defending champion Jordan Spieth threw the 80th Masters wide open on Saturday, even though Rory McIlroy suffered a hugely disappointing third round at Augusta National.
McIlroy began the day just a shot off the lead but evoked memories of his final round collapse in 2011 as he stumbled to a 77, failing to card a single birdie for the first time in 81 major rounds.
However, playing partner Spieth also bogeyed the 17th and double bogeyed the 18th after wild drives to card a 73 and finish three under par, just a shot ahead of fellow American Smylie Kaufman.
The 58-year-old Bernhard Langer was just a shot further back alongside Hideki Matsuyama and in contention to become the oldest major champion ever by a decade, with world number one Jason Day, Dustin Johnson and England's Danny Willett on level par.
Lee Westwood, Soren Kjeldsen and Brandt Snedeker were a shot further back, with McIlroy five shots behind Spieth on two over as he looks to complete the career grand slam.
"I climbed back nicely to get two under on the day and I thought even par was a fantastic score in those winds when we were warming up," said Spieth, who still became the first player to hold the outright lead for seven straight rounds. "So two under with three to go and the wind at your side, I just got really wayward from there.
"I just have to absolutely throw it away, the finish to this round, pretend it's a new round, everyone is tied and you have to shoot the best score to win. (I have to) understand it's the position I wanted to be in after 54 holes and not think about the finish to this round."
Langer, who won his first green jacket 31 years ago and the second three months before Spieth was born, utilised all of his experience to shoot 70 and believes he can surpass the 48-year-old Julius Boros as the oldest winner of any major. Jack Nicklaus was 46 when he became the oldest Masters champion in 1986.
"I've been saying it's going to happen sooner or later," Langer said. "W e have guys like Davis Love, Vijay Singh and Fred Couples who are all long enough to win majors. I'm not in that category but I try to make up for it in others and tomorrow I'm going to give it my best. That's all I can do."
Spieth, who is looking to become only the fourth player after Jack Nicklaus, Sir Nick Faldo and Tiger Woods to win back-to-back Masters titles, began the day with a one-shot lead into the round and edged further in front thanks to a two-putt birdie on the par-five second, where McIlroy missed from eight feet having being forced to lay up from a fairway bunker.
It looked as though Spieth would give the shot straight back when he drove wildly into the trees on the third, but he punched out to the back of the green and got up and down for par, and instead it was McIlroy who bogeyed after his approach from a fairway bunker span back off the green and he failed to get up and down.
McIlroy sensed a great chance for a two-shot swing on the seventh with Spieth struggling to make par after driving into the trees and finding sand with his approach, but the Northern Irishman three-putted from 25 feet and saw his playing partner scramble a matching five.
Spieth was nowhere near the form which saw him set records for the most birdies (28) and lowest 36 and 54-hole totals last year, but was grinding out a score and birdied the eighth after pitching to four feet.
McIlroy had found another fairway bunker off the tee and had to settle for par to fall four behind, and then brought back memories of his collapse in 2011 by hooking his drive into the trees on the 10th.
Although the ball bounced out towards the fairway, the resulting bogey dropped him further behind and the 26-year-old's chances then looked to be over when he found water with his approach to the 11th after a risky second shot from the pine straw, only for Spieth to also make a double bogey after taking four to get down from short of the green.
Spieth bounced back with a birdie from 17 feet on the 12th and looked to be in command when he picked up further shots on the 14th and 15th to move four clear, only to give the chasing pack hope with a poor finish.