Matt Kuchar and Gary Woodland share the overnight lead going into the final round of The Barclays but Kevin Chappell was the big mover on the third day of play as he set a new course record.
Kuchar struggled to find rhythm as the sun finall shone in Jersey City, and two bogeys on the opening nine contributed to a round of one-under 70, allowing Woodland to move level.
Woodland might have taken a clear lead after four consecutive birdies on the opening nine, but he suffered on his way back with three bogeys limiting him to three-under 68 and letting Kuchar off the hook.
But it was Chappell who lit up the Liberty National with a round of 62, 10 shots better than his second round effort.
Starting on the back nine, Chappell birdied the 10th, 16th and 17th holes, but it was on the way back that he really lit it up, with four birdies in a row between the third and sixth holes helping to propel him from a share of 43rd place to third.
"My game hadn't shown much lately, but I've been working hard," Chappell told the PGA website. "It paid off today.
"I got some good breaks. I played from the wrong fairway twice, but took advantage of the breaks and holed the important putts."
Tiger Woods is in a share of fourth place alongside David Lynn after a round of 69 left him four shots off the pace.
The world number one has been battling back pain this week, and was happy enough with his round under those circumstances.
"It starts off great every day, and then it progressively deteriorates as the day goes on," Woods said of the pain in his back.
"Hopefully tomorrow it will be one of those days again and fight through it and see if I can win a tournament.
"Unfortunately I had two three-putts, but other than that, I felt like I really putted well and made my share of putts."
Also in that group is former leader Webb Simpson who went from a second round 66 to a third round 74.