Paul Casey will take a three-shot lead into the final round of the Deutsche Bank Championship after he fired his third consecutive 66 at TPC Boston.
Casey recovered from a sluggish start to reel off three straight birdies from the fifth, and he added another birdie at 16 to claim the outright lead before coming within an inch of a sensational albatross at the last.
The Englishman's 232-yard second bounced short of the green and hopped onto the putting surface before veering towards the hole, his ball narrowly missing on the low side and settling two feet away from the cup to set up a tap-in eagle.
Casey's grandstand finish took him to 15 under for the tournament and put him in prime position to collect his first win since 2014, and his first PGA Tour title since making his breakthrough in the United States at the 2009 Shell Houston Open.
Brian Harman emerged as Casey's closest challenger after the left-hander birdied two of the last four holes to complete a solid 68, while PGA champion Jimmy Walker is a further stroke adrift along with fellow Americans Kevin Chappell and Smylie Kaufman.
Chappell, playing alongside Casey, had looked on course to claim the 54-hole lead when he hit back from a bogey at the third with birdies at the fifth, eighth and 10th which lifted him to 13 under.
But he endured an unlucky break on the 12th when his perfect tee-shot ended up in an awkward lie in a big divot and his second spun back into a dry hazard, from where his escape attempt cannoned off a rock and flew over the green, 60 feet from the flag.
He took three more to get down and could only par the final six holes to remain on 11 under, with the in-form Ryan Moore one shot further back after he carded a bogey-free 68.
Former Open champion Louis Oosthuizen vaulted 47 places up the leaderboard with a superb 64 - comfortably the low round of the day - which featured four straight birdies from the second and two in three holes after the turn.
Oosthuizen rolled in his seventh birdie putt of the round at the last to take the early clubhouse lead on nine under, where he was later joined by a resurgent Rory McIlroy and Olympic champion Justin Rose.
McIlroy continued his recent improvement on the greens as he offset an opening bogey with a birdie at the second, and he was soon threatening the lead when he carded four birdies in a row from the fifth.
But the world No 5 again came to grief at the 12th, where he ran up a triple-bogey in the first round, pulling his second long and left and being forced to take a penalty drop before getting up and down from the fringe to narrowly avoid another seven.
McIlroy bounced back with a 10-foot putt for birdie at 15, and he came even closer than Casey to signing off with an albatross-two at the last - his 210-yard long-iron catching the lip of the hole and leaving him a tap-in for eagle and a round of 66.
Rose was not at his fluent best, but he did birdie the final two holes to salvage a 69 - his third sub-70 score of the tournament - while current FedExCup leader Patrick Reed struggled to make much happen in a 70 which included two birdies, one bogey and 15 pars.
Open champion Henrik Stenson was two over for his round before he birdied 16 and drained a 20-foot putt for a closing eagle to sign for a 70, five under for the week alongside Jordan Spieth, who bogeyed the first three holes and also took six at the 12th in an erratic 72.
World No 1 Jason Day was another player to close with an eagle three, but a 68 merely lifted him from the foot of the field to four under - 11 shots behind Casey.
Due to expected bad weather at TPC Boston on Monday, live final round coverage will now begin at 12:30pm on Sky Sports 4 - your home of golf.