American Keegan Bradley sunk a birdie on the 18th to leapfrog Adam Scott and take a one-shot lead following the third round of the BMW Championship.
Bradley made the most of a rollercoaster day, splitting eight birdies with six bogeys to card a two-under 70 and head into the final day at Castle Pines Golf Club on 12-under par.
He overtook Scott for the top spot on the final hole, with the Australian struggling to a third-round score of 74 - with two late birdies helping him keep in touch with Bradley.
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Speaking after his round, Scott said: "I felt like I made a meal of that, and I didn't feel like I did that much wrong - a couple of drives were just not quite right, and a three-putt, and all of a sudden I'm chasing.
"I'm in a good spot at the end of it to be one back."
Clubhouse leader Bradley believed his fighting spirit prevailed in challenging conditions.
"It was tough out there today," the Team USA Ryder Cup captain admitted. "It was really windy, a lot of elevated tees that were into the wind, which makes it really tough.
"Proud of the way I fought today. I played some brilliant golf but I hit also some terrible shots, too. I guess that's the way of the world. But I'm proud of the way I fought there in the end.
"I told myself after those three bogeys in a row that I was either tied for the lead or maybe one back... I really hit quality shots coming in after that."
The Swedish duo of Ludvig Åberg and Alex Noren are tied for third on 10-under par, after carding 71 and 70 respectively.
American Xander Schauffele is three shots further back on seven under.
How can I watch the FedExCup Playoffs?
Every event is live on Sky Sports, with early coverage from the BMW Championship third round starting on Sky Sports + at 5.15pm. The action picks up on Sky Sports Golf at 7pm, following the conclusion of the AIG Women's Open on Saturday.
Sky Sports+ has officially launched and will be integrated into Sky TV, streaming service NOW and the Sky Sports app, giving Sky Sports customers access to over 50 per cent more live sport this year at no extra cost. Find out more here.