Jason Day finally hit the wall but countryman Matt Jones rose to contention going into the final round of the US PGA Tour's second playoffs tournament.
Needing to win to claim the world No.1 ranking this week, a weary Day shot a two-over-par 73 third round to fall nine shots behind leader and former champion Henrik Stenson in the Deutsche Bank Championship.
It was world No.3 Day's first over-par round since the final day of the US Open back on June 24, ending the hot streak that brought him three titles, including a major, from five tournaments.
The Australian never overcame a double bogey on the fourth hole at TPC Boston, adding bogeys at the par-3 11th and 16th and another at the 14th on Sunday.
"There's no excuse for poor playing," said Day.
"I just wish I had a little bit more energy."
Young American Jordan Spieth is now set to reclaim the world No.1 ranking from Rory McIlroy this week despite missing the cut for a second straight week.
While Day failed to fire, the in-form Jones put himself in with a chance of taking his second US tour title on Monday (Tuesday AEST).
The 2014 Houston Open winner shot a 68 to get to 11-under, two shots behind leader Henrik Stenson (65), one behind American Rickie Fowler (67) and tied fourth with Sean O'Hair (67).
Jones has been on the leaderboard several times in recent months, including leading at the halfway point of Day's US PGA Championship at Whistling Straits.
Jones, who started with birdies on three of his first four holes, was in a three-way tie with Fowler and Stenson at 12-under down the stretch, before a slip up at the par-three 16th cost him.
The 35-year-old found a bunker from the tee and was unable to get his shot anywhere near the pin, before two-putting for a bogey.
Things threatened to unravel further on the par-four 17th when he missed the fairway to the left and found himself in a heavily wooded area, right behind a tree, but he managed a miraculous escape.
Jones played a low, hooked punch into the green, heavily hooking the ball around and onto the fringe, before making a two-putt par.
Stenson shot a bogey-free 65, including an eagle at the par-four fourth when he drove the green before holing a 20-footer.
World No.8 Stenson won the Deutsche Bank in 2013, before going on to win the Tour Championship and claim the Fedex Cup.
"It's always good to be back at a course where you've performed well and played well," Stenson said.
"I'll just try to keep it going."
McIlroy was well out of contention at two-over for the tournament.
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